I own it's baby brother, the TSA5. I think it's absolutely awesome, and can't see why the 15 isn't so much better, and louder!
If I was in the market, I'd definitely look at it.
Here is my TSA5 on top of my Marshall G15RCD.
5W of all-tube power, 1x 12AX7 and 1x 6V6GT.
It has a very basic control setup, with a volume and color (which is basically tone). When turned to about 1/4 of the way around, you get a Fender Champ vibe. Keep going, and it gets sharper and more shrill, eventually getting some really good tube breakup and sounding like a screaming banshee!
Hit the switch for the onboard Tube Screamer, and you have all out apocalyptic war in a tiny box.