I was in the exact same position as you in my draft this weekend, #5 in a 12-man draft. Here's how it played out:
T.O. was gone by the 16th pick. The way I see it, Jones at the 29th pick could be the move that will win fantasy squads championships this year. My reasoning on that is that he'll likely be selected somewhere between the 18-20th RB off the board at that position. If you look to last year's 2003 fantasy season, you can see what players ended up with to receive the 18-20th end of season ranking:
#18) Barber, Tiki RB NYG - 278 att, 1215 yards 4.4 YPC, 2 TD, 69 rcpts, 461 yards, 6.7 ypc, 1 TD, 6 FL, 152 fantasy points
#19) Martin, Curtis RB NYJ - 323 att, 1308 yards, 4.0 YPC, 2 TD, 42 rcpts, 262 yards, 6.2 ypc, 0 TD, 2 FL, 152 fantasy points
#20) Barlow, Kevan RB SF - 201 att, 1024 yards, 5.1 YPC, 6 TD, 35 rcpts, 307 yards, 8.8 ypc, 1 TD, 4 FL, 146 fantasy points
Based on this, all you need to do really is convince yourself that Thomas Jones is a lock for equivalent fantasy production in 2004. Based on what's coming out of the preseason, I don't see why that isn't easily possible, but with the upside to far exceed that type of production. I am convinced that Thomas Jones can at least produce enough to warrant him as the #18 RB but has plenty of upside to him that could see him finish much higher than that by year-end.