It's often said that gear will never make you sound better than you are. It's all in the fingers. And this is true, the one and only exception I've ever come across being the Strymon Deco.
I mainly use the left side, adding saturation to edgy cleans, and it really does make me sound better than I am. The harmonic richness the pedal adds is subtle, but amazing. Switch it off, and you notice it's gone. Then your foot goes back down and switches it back on again, perhaps to never switch it off.
The way I'd put it is that a nicely dialed-in guitar without it probably gives me a thrill 90% of the time, but then I hear the odd chord or note where the tone sounds too bright, or too dull. Switch on the Strymon and the 90% that was already good sounds better and most of the 10% I didn't like is gone.
There's lots to play with on the right hand side as well, but to be honest, edge of breakup cleans are mostly what I want, so I sometimes use the right hand side as a chorus, which is nice in that it's a good chorus that saves me an extra pedal.
The chief con is the price. I would say it's worth it in terms of the value it adds, but it is expensive.