i JUST got a new head to replace my svt 3. I could never get the thing to sound the way I wanted. I take a lot of responsibility for that, as I'm not exactly an expert on sound...but everything seemed so touchy on that thing. The underpowered part I tend to agree with, although some of the trouble was the result of running it at 8 ohms instead of 4. At 8 ohms it was way underpowered for outdoor or larger indoor gigs and the sound quality really really suffered when I tried to push it.
Despite some of the reliability concerns people claimed about the mesa boogie m9 carbine (when it first came out anyway) i layed some money down for that. The extra power it has at both 8 ohms and 2/4 ohms have made it a ton easier to find a tone I'm happy with. So far, I love the m9 compared to the svt3 and if the reliability issue has definitely been resolved, then it's not even a competition between the two.
All in all, the ampeg served me well, and I'm sure it will do well for anyone on here that has one, but I just struggled with it a lot.