Well, after being on the American marketplace for 1 week the demo was opened up to Silver members today so got it downloaded with my US profile.
My first impressions, brilliant, I'm one of the few that really enjoyed Untamed but this is a huge step up in terms of gameplay, physics, graphics, pretty much everything.
If you're like me and can't stand those racing games where you struggle to get your vehicle around corners then you should love the controls in Reflex, using your body weight independantly(using the right stick) from steering you can really chuck your vehicle into the corners, very fast and responsive steering and although not easy to get the hang of, I think it's just superb!
AI is definately improved, in Untamed you always seemed to come off worst from the slightest collision with the AI(and with 12 riders on the track there are plenty of them at times) but this time around it seems much fairer, with them taking the brunt as often as you,also the fact you get the chance to recover bad landings takes away alot of frustration and is pretty rewarding when successful
Track deformation, I loved it in Sega Rally and I love it here too, should make for some really fun online games, especially over several laps.
As for graphics, more gritty and realistic looking than in Untamed, much more of an improvement than I was expecting to be honest.
Definate release day purchase for me, sadly while it gets released next week in the US, it has already been confirmed by THQ that this release will be region-locked

so February 2010 it will be(the official UK release date).