I own this bike and have put a little over 1,000 miles on it since I bought it late this summer. The tires that came with it lasted about 400 miles...but they did look cheap. The tire size is 700c x 28....you could easily fit 700c x 32 on the rims with no problem if you like a slighty wider tire....All that depends on what type of trails you are riding on.
I replaced the stock tires on this bike with a set of Serfas Seca slicks....cost 25 each at the LBS....Good tires...great traction on the dry and wet pavement. Good flat protection too.
What type of riding are you going to be doing...what is the surface like. If it is pavement this is a great bike...its fast...and handles solid. Well worth the 250 bucks IMO.