There's not too much of a difference between the build on the '05 and '08 track pros, just bars, stem, and seatpost.

I'd say to go for the '05 because you're basically getting the same bike for cheaper and the paint job is nicer IMO.

I have an '07 track pro that gets ridden on the street and track, it is a very stiff frame so you will feel the bumps in the road which takes some getting used to, having such a stiff frame on the track is nice though. I've done 100+km rides on the street with it with no problems, the frame is responsive and it accelerates quickly, you can feel your power getting transfered to the road without the frame taking power away.

I like this bike a lot for riding on the street and track but it's not for everyone, if you want a smoother ride with more vibration dampening for rough roads go for something with a steel frame instead.