Clean 1 is a warm, VERY clean mode, which can often sound a little muddy, but after taking some time tweaking it, you'll find some good tones. Clean 2, is modelled after the JTM-45 clean, and has more top end. This is what I predominantly use for my cleans. It's more crisper with more presence. Again, it will take some time dialing it in, but it can be done. The OD 1 can range from a plexi lead all te way to a hot-rodded JCM800 with the bass shift on and gain maxed out. The OD 2 is primarily voiced differently, with more emphasis on the mids, AND with an extra kick of sustain and gain. There's more gain on this mode than any other Marshall, and arguably any other amp out there. It's pretty wild. Think more like a JCM TSL or DSL, but better. Once again, it does Marshall very well, but ONLY Marshall. Don't expect it to do anything else. Think Marshall tone with more gain than previously seen. I would suggest against maxing the gain to 20, because the sound will most likely turn to mush, unless you playing an unltra searing lead, etc. Also, if you're gonna go with this unit, couple it with a good tube power amp. It will sound like it's meant to sound. I'm playing either an Ibanez RG-270 with EMG's or an ESP Lynch Custom with Duncans into a Boss SD-1, Crybaby Wah-wah, into the JMP-1 - Rocktron Hush IICX - TC electronic G-Major - BBE 362 Sonic Maximizer - Mesa 50/50 driving a Marshall 1936 2X12. If you're expecting to this unit to single handedly provide you with great tone, like putting it with a power amp into a cab alone, then you're likely gonna be disappointed. It's merely a preamp. It will provide great tone, BUT will really shine with an FX processor in series, or at least a parametric EQ. You're tone shouldn't rely too much on one piece of equipment. It's the system as a whole which gives me my tone, and I couldn't imagine it without any one item or unit.
I recommend it if you're planning on using a good TUBE power amp, Mesa, Peavey, etc. and either a parametric EQ and/or an FX processor. My TC G-Major really works great with the JMP-1. It does a great job for me personally. Don't expect it to sound great on it's own though, without any effects. And don't expect it to do anything other than Marshall. Otherwise get something else.