Just received my j-22 today, so these are my immidiate impressions.
Have only tried it out with my telecaster and in terms of tone, headroom, dynamics, it's seriously good! Highly usable, very inspiring. You can really dig into it and it can be quite loud if you need it to. I prefer to push the (fantastic) reverb and perhaps just dial in a tiny splash of chorus. Bought it for that signature clean, not the chorus effect - fun to play around with though ; to add some colour to the sound, some airyness / width. I'll be using it at home for writing and recording. I have no doubt that you could gig with it though! It really has a full, loud voice - and does not get muddy when you crank it.
The only things bothering me: the infamous hiss of this line of amps is not too bad, but its there. And when playing it with my tele, just touching the strings gives a slight static "umf". This COULD be the guitar though.. or me being used to a small digital amp. All in all, its really a great amp for anyone who values a great clean tone. Highly recommended.
After almost two years of use: Still really loving this amp! It has proven to be an almost perfect clean platform for all my guitars, including Telecaster, Sheraton ii, Les Paul Jr. and a Firebird. All guitars sound true to their specific character through this amp, articulate and uncoloured. The same thing goes when using several pedals through the frontpanel input. Its honestly hard to find something noticable that I really dislike about this little amp.. No regrets!