It always comes back to size. Pack in as much functionality as you like, but pocketability and sheer dimension-squeezing, can't-believe-it design will always get heads swivelling and wallets opening.
Samsung's Ultra range, of which the D900 is a debut member, boast extreme slimness as their headline grabber, with two breaking records on account of their waif-like measurements.
The handset on test here is - currently at least - the world's slimmest sliderphone at an astonishing 12.9mm thin, yet still manages to cram into its svelte casing a digital music player and 3-megapixel camera, plus a feast of mobile functionality.
Slim it may be, but the D900 doesn't go shouting its vital statistics from the highest building. Indeed, to look at it front on it's a fairly regular Samsung sliderphone handset with the usual array of navigational tools on display.
It's got Samsung's standard four-way joypad with central selector key lies beneath the imposing screen, flanked by two soft-keys, call and end keys, and a cancel button.
Dominating the handset, the 2.1-inch screen is resplendent in its deep black setting, which only serves to accentuate its clarity. Samsung has also made the most of the 12.9mm depth, with a camera shortcut key located on the right-hand side along with the headphone/charging port, and a volume rocker next to a microSD card slot on the left. That's some impressive use of not much space!
Sliding the handset open using the neat raised bridge avoids sticky finger marks on the screen, and reveals a white backlit keypad that sits flush in the casing beneath. Individual keys utilise the handset's extra width, and are both well-spaced and perfectly sized for regular use.
While much is made of the D900's slimline proportions, what's perhaps more impressive is the fact Samsung has somehow managed to squeeze in a 3-megapixel camera with auto focus in amongst its feature-set; not bad when you consider the weighty bulk of other 3-megapixel shooters.
Pressing the camera shortcut key will take you straight to the imaging menu, where you're given the option of shooting stills or video clips, and viewing previously shot media. Extensive options are on offer when it comes to settings for exposure, white balance and ISO, and several effects can be applied to both camera shots and video footage.
Basic image editing can also be carried out in-camera from within the Image Editor application, or using the programs contained in the PC Suite.
Shooting video is given added versatility by the ability to pre-set the length of shot according to its intended distribution method. For example, if you're only interested in sending MMS clips to your mates after a night out then simply choosing 'Limit for MMS' will configure the settings appropriately.
'Normal' will leave you free to shoot up to the constraints of your memory card at whatever quality setting and image size you want up to 352x288 pixels. Unfortunately, utilising memory over and above the built-in 80MB store is down to you, as no microSD comes bundled. Nonetheless, with cards getting cheaper all the time, this is no major problem.
Getting a decent sized memory card will also serve you well for music. Although there's no quick-access button or dedicated transport controls, press the 'down' button on the joypad and you'll find it pre-programmed to take you straight into Samsung's Music Player app. This can be operated with the handset open or closed, and handily the volume rocker remains active even when the keypad is locked. Of course, calls take priority, so your music will always be interrupted should someone want to get hold of you the old-fashioned way.
File-types shouldn't prove too much of an inconvenience, with MP3, AAC, ACC and eAAC all catered for. Transferring tracks is as easy as drag-anddrop, thanks to the fact the handset is recognised as a mass storage device when hooked up to a PC via the bundled USB cable.
Alternatively, you could make use of the excellent Samsung PC Suite to manage your music. Navigating playlists is similarly straightforward, employing the same drop-down menu layout as used throughout the menu.
Rounding the handset off is a selection of tools to help you keep on top of your affairs, the most useful being Picsel's File Viewer application. There's also the standard calendar, memo and time-keeping assistants, and finally a voice recorder function for making voice notes.
With its initial Ultra lineup, Samsung has been content with letting the dimensions speaking for themselves rather than adding major design embellishments. This looks like a regular Samsung sliderphone, only it's thinner - but none the less, this is a quality handset packed with excellent features.
The camera performance is, as you would expect from a 3-megapixel affair, outstanding in most aspects, bar a slightly sluggish shutter release.
Remember, though, if you want to take advantage of the highest quality settings you'll soon use up the generous 80MB of onboard storage so make sure you invest in a hefty memory card. We'd also advise you go for the 'standard ratio' format viewfinder, as full-screen can make accurate framing difficult.
Video features were also pretty impressive, and it's good to get the chance of showing them on the telly thanks to the TV-output. Given the limitations of the format, footage recorded in MPEG4 at the highest quality was relatively free from judder and pixilation, and colours were rendered accurately.
A small gripe would be the lack of a full-screen playback option, but this is a minor concern given the overwhelming positives of this handset's imaging prowess.
A further bonus is the quality of the accompanying PC Suite. So often an afterthought, Samsung has put real effort into designing software that allows for all kinds of file management processes, as well as image manipulation and video editing to make the most of the camera facilities.
Call quality is nothing short of excellent, boosted by Samsung's 'voice clarity' feature, and music playback is also good through the supplied stereo headphones. Things are further improved by the 3D sound setting, combined with a bit of tweaking of the equaliser. Battery life, however, was a touch disappointing - we got on average around three days' use out of the phone.
Overall, the D900 is just as happy in a business environment as it is accompanying you on the party circuit, and Samsung should be applauded for its conviction that style and functionality don't have to be mutually exclusive concepts.
Memory card support: Despite its thinness, Samsung has still managed to slip in a microSD card slot on the side of the phone
Camera: A high quality 3-megapixel camera is built in to the back panel of the handset
Slider: Smoothly slip up the screen and the phone's alphanumeric keypad is revealed
Ultra thin: At under 13mm, the D900 is the slimmest sliderphone currently on the market