Awesome!
Wow, such a simple concept but pulled off brilliantly. I love the graphics, the gameplay, the achievements, the upgrades, absolutely everything is amazing to play.
Also, for those seeking the magic 6000ft mark, i will give you a hint: fuel ;-) you should be able to figure it out from there. Oh and on that note, getting the 6000ft achievment would be much much cooler if you got something at the end rather than just the cutscene.
But yeah, to summarise, it is one heck of a game =P