It's not unusual for companies to release tie-in gaming peripherals with popular games. What is unusual is releasing peripherals long before the game is even out, but with the SteelSeries Diablo III Mouse this is exactly what has happened.
It could be seen as a bit of a gamble on SteelSeries' part - Diablo III is still around a year away from release, so there's some uncertainty about how it is going to be received. However it's a game made by Blizzard - the company behind the hugely successful World of Warcraft videogames, and with the popularity of the previous instalments in the Diablo series, this risk isn't really that big.
The SteelSeries Diablo III Mouse is essentially a re-skinned version of the SteelSeries Sensei Pro Grade Laser Mouse. If you don't have one of these, then this is no bad thing.
It's comfortable and responsive, with an ambidextrous design that works well in either hand. There are a number of differences between the Diablo III Mouse and the Sensei Pro Grade Laser Mouse, however. To begin with, there's the Diablo III branding, and unlike the SteelSeries World of Warcraft MMO Gaming Mouse: Legendary Edition the branding actually looks very nice, with the design understated in some places.
If it wasn't for the presence of the Diablo III icon, which naturally pulses red when plugged in, it would make for an attractive mouse regardless of gaming preference. The finish is also a pleasingly matt rubber - a very nice change from the SteelSeries Sensei Pro Grade Laser Mouse's shiny, plastic case.
Another nice change is the middle scroll wheel, which is now ridged, giving the appearance of scales. It looks good, but it also functions well by giving you greater control over scrolling. It does lack the built-in LCD menu of the Sensei. This might not have been essential, but it was useful for scrolling through various preset modes.
Overall, the SteelSeries Diablo III Mouse is a great gaming mouse that is comfortable to use, and even with the Diablo III branding it still looks good no matter what you're doing or playing.