I think this number is very fair. A couple weeks ago some sites I looked at had the number around 41 which I would have jumped on, and been a little insulted. This is much more realistic, and a very tough number to go one way or the other on.
The Bucks won 46 games last year as an overachiever. Overachieving teams usually take a small step back. But the Bucks added some pieces that should make the team better with Corey Maggette, Drew Gooden, Chris Douglas Roberts and Jon Brockman. The Bucks will also get a full year out of John Salmons, and nothing from Michael Redd, those two things alone should be a bonus.
With the nucleous of the Bucks being young players that should only get better I think the additions plus the experience gained last year should make up for the over achievement of last year. Which puts us right back to 45-47 wins.
If I had to bet my mortgage I would bet on the under. Since it is a fair number I think it is more likely an injury or two will bring the Bucks down a few wins from last year than the team winning almost fifty games. Look at it this way, with the current roster is it more likely they can win 50 games or that a player or two(Bogut) will go down and the team will be closer to 40 wins?
I would argue it is more likely the Bucks could get a little unlucky this season, but still be good enough to get to over .500 and into the playoffs.