An UNMODDED SLO would be my only amp if it weren't so fricking loud. And it does need to be loud to sound it's best. It gives me everything I want out of an amp : it has plenty of gain, maintains note articulation and separation, leads cut through, palm mutes thump, I run the pre on the OD channel around 7 and it still cleans up great when I roll the volume down...this allows me to use it as a single channel amp that can be clean, crunchy, or screaming. I'd say it can be a little unforgiving compared to some amps. Though, it's nowhere even close to being as demanding of a great player as the Astroverb. Is the SLO less versatile than other amps? If it is, then it means you are not using it properly. Most amps are dumbed down with multiple channels because many people can only get 1 tone out of a single channel amp. That's not the amp's fault. If you want it to sound like a Mesa Boogie...well, it won't. You would be best off buying a Boogie. If you want a Marshall sound...well, the SLO shares some characteristics with a JCM800. But it is NOT the same. Both can be "out front"/in-your-face amps that can't be ignored, especially if you are a lead player. But the SLO does have a distinct Soldano sound, like a Marshall has a distinct Marshall tone.
Let me point out, the SLO is the perfect amp for me. It works for me. Because you're not me, it might be all wrong for you. So I'm not sure if any of this will be at all useful to you.