If anything, Stubbs defense should improve further as he becomes more familiar with the parks in the league.
I think his offense is anybody's guess. My hunch is that he will hit in the .260's with 12-18 HRs. His primary job though, is to get on base and put pressure on the opposition's defense....the job that Taveras failed to achieve last year. If he succeeds, and I suspect that he will, and plays gold glove defense, he will be an above average CF'er.
This thread gives the impression that the Reds offense is in intensive care. I disagree. I think the only real need offensively is a good #2 hitter. That spot was abysmal last year. Having a solid hitter in that spot will improve Stubbs's offense and set up a decent string of power in the middle of the order.