The game works in both vertical and horizontal modes, although if you use the horizontal mode on the N95 or N93/N93i you will have trouble playing the game. The speedometer is designed for the E90's wider screen, and on a narrower 320x240 format it blocks out the action. 240x320 works perfectly however, and it was probably designed with the E90's external screen in mind so that people could play the game with the E90 closed as well as open.
According to the developers' website, an official release of the game across all S60 3rd Editions will take place later this year, although of course the graphics probably won't be as smooth on phones that don't have the 3D acceleration hardware.
You can see the official E90 Global Race trailer here. There's also an unofficial video review of the game in action on an E90 here.
There's a video of Global Race on the N95 on the Unofficial Nokia Gaming Blog.