For years I've played on Chessmaster and it was the only program I was using for a long time and I never found glitches in the Personalities that came with the game. They are challenging enough depending on the Personality you're playing against. But a couple of weeks ago I got Fritz 12, and after being an advocate for the CM series, I've moved my loyalty over to Fritz. It's a stronger, deeper program than CM. But I do keep CM around for my chess league that I have, so it's still being used.
In chessmaster

I think playing against chessmaster is a great practice.
playing against lower rated opponent in chessmaster is the best practice. since the opponent will give you some sort of advantage and you will have to learn to convert the advantage to a win.

Chessmaster is buggy (enough so that I vented a couple of complaints about CM about a week ago, and decided to stop using it altogether), but I doubt anything is being done about it. Ubisoft seems more interested in pushing their other, darker, more violent games. They also have a terrible tech support department.

Maybe when I will defeat chessmaster (which defeated GM Christiansen) then I will buy a better chess engine.
I really don't know why so many people below 2400 rating buy Rybka(now with Rbyka 4) when Rybka 3 couldn't be defeated not even by the best players in the world.

for beginner players: lessons and exercises and playing against the computer - i think chessmaster is great.
for above average players or higher: analysis of games and playing against the computer - i think fritz or rybka is better than chessmaster.

I only wish there was a version for mac. I left my copy of chessmaster in the U.S. and now I only have a MAC.
As for bugs, there are some cute things in it when playing blitz. I noticed that the 1300 rated player could beat Kasparov in a blitz game.

for beginner players: lessons and exercises and playing against the computer - i think chessmaster is great.
for above average players or higher: analysis of games and playing against the computer - i think fritz or rybka is better than chessmaster.
what do you mean in game analysis?
i like both game analysers from chessbase to chessmaster

what do you mean in game analysis?
i like both game analysers from chessbase to chessmaster
fritz and rybka engine analysis is much stronger than chessmaster's imho.
that being said, for beginners, chessmaster may still be better for game analysis because it explains the moves more than fritz or rybka.
do you guys think chessmaster (since 10th edition) has bugs in rating bot players to play with?
I saw many people saying that this thing is worthless.
What do you think?