Sorry, but in my book this will never compete with Trackmania. The time and skill dropoff between the basic editor and the advanced editor just looks way to big, nothing could be better than the concise simplicity of Trackmania's editor. And about the racing part, its fun to crash and play road rage when racing with friends but when it really come down to it Trackmania will always be awesome just because in the end its the play with the most skill who wins, not the player with the best car or the player who got lucky and didn't get caught up in a huge car pile-up. I just don't see this game becoming as big as Trackmania.
It could get big depending on how they advertise it. Advertising can do wonders for a games initial sales.
I'll always be true to Trackmania but I'll likely give that one a try as well. I like games with a map or track editor. I doubt I'll ever stop playing Trackmania though. It's the one game that I find has an endless replay value.