The JM4 arrived today so here is a very, very, very quick review.
It's being sent back tomorrow. I tried it for a few hours and just didn't like it - the modelled sounds are just too digital for my liking (I guess I should have known this beforehand!). The jam tracks are pretty good fun and probably very good for practice and timing but for £209.00 I didn't think this feature justified it. Mic'd up it sounded pretty decent but it's not very often that I get to mic the amp up and play at a decent volume.
Basically if felt like something I would use for a while and then sell for half price on eBay in a few months time - this made my mind up for me.
There you go - very quick. Already planning what to spend that £209.00 (minus postage) on now!