don't get tires less than 35. wider tires give a more comfortable ride and corner better. unless you are a racer doing 20 mph + all the time, you will not notice a difference in speed from a 35 to a 28 but you'll see a big difference in smoothness on the trails. make sure that the bike fits you very well. nothing is more important than fit otherwise your back, hands, neck will hurt and you'll want to pedal harder or longer but can't. some shops wont but two shops near me offer free fitting (on a trainer for 30 minutes) with the purchase of a bike. this is something to look for. when you test ride a bike, make sure the lbs properly inflate the tire and raises the saddle to an appropriate height for you. make sure that the stem has no more than a 10 degree rise and is 100-120 mm length. 1-2 miles is not a very long distance. if you didn't want to do trails i think you'd have been fine with a cheaper bike. if you live in a flat area then you don't need fancy derailers. if you live in a hilly area like me, then a 9 speed (= better shifting) system like deore or x5 is worth it.
keep in mind that the 2011s are on the way...look for a discount on the 2010 or in my case wait for the 2011 which have better specs, similar price = better value
trek marlin 29er mtn bike 2011 $470: good frame, decent wheels. downside is it's not released till august.
http://www.trekbikes.com/us/en/bikes...rdtail/marlin/
specialized rockhopper 2011: $630: drive train is very nice for the price. if you live in a flat area then you don't really need it. because you're only commuting 1-2 miles, 26" won't be a problem. they're a little slower for commuting than 700c or 29ers (people debate this endlessly) but for your short trip you won't notice difference.
http://www.specialized.com/ja/en/bc/...nuItemId=14121
trek 7.2 fx 2010 $480: frankly i think the marlin is a way better value.
but make sure you get the best fit! most important. standover is that important but straddle over the top tube and should be able to lift the wheel 2". if you have to, you can give up a little bit of SO but make sure you buy the right bike with correct effective top tube length
make sure that the steer tube is not cut too low and that the handlebars are too low. honestly, for comfort, the handlebars should be level or higher than your saddle (rivendell's philosophy). others will disagree but that's how i feel. if your handlebars are too low due to geometry or cut steerer, it can hurt your back or you'll feel scared on a descent because you can brace yourself behind the handlebars as well as if they were higher up.
good luck!