Updated: read our early Hands on Nokia N900 review.
The main difference is it's using the Maemo OS, which has been reserved for Nokia's internet tablets before, but now makes its debut in a phone-sized chassis.
It's the same slide-out QWERTY form factor as the N97, but the N900 has a more responsive screen, a keyboard more similar to the E75, and crucially a new UI too.
Maemo not only means better multi-tasking (with 1GB of memory supporting a huge amount of applications) but also brings Mozilla's internet browser to the masses, complete with full Flash 9.4 support.
It's running with a super-powerful ARM Cortex-A8 processor and OpenGL ES 2.0 graphics acceleration under the bonnet, and also brings a 5MP camera, 32GB of internal memory and ultra-fast 10Mbps HSDPA download speeds (if your network supports it).
The Maemo interface is completely redesigned as well to allow multi-tasking, with movable icons, an upgraded and more attractive UI, as well as more desktop-style applications.
The N900's screen has a higher resolution than most previous Nokia phones, coming in at a WVGA (800 x 480) pixel count, so video watching will be a breeze.
Cheaper than before
"With Linux software, Mozilla-based browser technology and now also with cellular connectivity, the Nokia N900 delivers a powerful mobile experience," says Anssi Vanjoki, Executive Vice President of Markets for Nokia.
"The Nokia N900 shows where we are going with Maemo and we'll continue to work with the community to push the software forward. What we have with Maemo is something that is fusing the power of the computer, the internet and the mobile phone, and it is great to see that it is evolving in exciting ways."
The new phone will be shown off at Nokia World next week, where TechRadar will be getting an in-depth hands on with the device, and has a release date for later in the year at the pretty reasonable sum of €500 (£440).