Why wouldn't you play this game?
controls are very unique and can even adjust your lean down to the angle degree. there aren't many modifications other than the exhaust but if you think about it, there's not much you can do to a bike unless you want to committ suicide. i can understand why polyphony left that stuff out. over the top modifications also throw off the balance of the bike which turns it into a 2-wheel death machine. another fun tid bit is the ability to change your riding suits. you can have 2 sets of racing and 2 sets of street suits. you can change your helmet, jacket, gloves, pants, and boots. the courses are the same as GT4 which is alright because you'll be glad you know what the course is like when it comes race time. the bike gaining aspect is a little strange since there's no money but you'll find it rather easy to get the bikes you want.
overall i'd say it's a very good game. there aren't many motorcycle simulators out there. just playing this game puts a smile on my face. especially when you win a race and then the computer takes over and crashes.