I think the positives for Maggette outweigh some of the negatives that have understandably been mentioned.
I may have missed it, but I don't recall Maggette having been a particularly bad guy in the room or having done anything embarassing off the court. He has that Duke pedigree, even if only for a year, and has played for a relatively demanding coach in Dunleavy -- it would be virtually impossible to simulate the Popovich hard line, of course, but there are signs that the kid responds to good coaches.
I think the injury thing is a problem, but I'd be interested in finding out the nature of the injuries he's sustained over the years before deciding that he's just simply unable to play more than 70 games and is iffy to be ready for a playoff run.
I see an inherent upside to Maggette's experience -- an upside that outstrips Pietrus, Azubuike, or Smith -- in that the Spurs are trying to win now and don't need too many guys who are still trying to learn how to play in the league. Maggette has the respect of officials, he's 9 years in, and he's played relatively well in a number of systems. I somehow find all of that to be more reassuring than troubling in thinking about Maggette as a Spur.
The thing that kills me is that even having missed a relatively high number of games in each of the last few years, Maggette has finished those seasons in the top 10 in FTA:
2003-04 -- 73 games, 620 FTA (3rd in NBA)
2004-05 -- 66 games, 657 FTA (8th in NBA)
2006-07 -- 75 games, 633 FTA (6th in NBA)
2007-08 -- 70 games, 681 FTA (6th in NBA)
Those are remarkable numbers if you stop to think about it. He's also done that without playing some ridiculous number of MPG in those seasons (36.0 in 03-04; 36.9 in 04-05; 30.5 in 06-07; and 35.7 in 07-08). I know his ability to get to the line has been discussed over and over in this thread, but the extent to which those numbers illustrate his ability to do that is pretty astounding. If you think about it, there's a decent chance that even playing the reduced minutes that the Spurs might impose upon him, Maggette could be among the top 10 in the league in FTA. The Spurs haven't had that since 03-04.