So I recently sold all my pedals (not saying much) to buy an ME-50 and a footswitch for the extra functions. Here's the way I use it and some observations on its sounds and function.
I very nearly gave up on this due to the silences when changing memory locations and the usual volume inconsistency between patches that takes so much tweaking time on a multi effect but now we've come to an understanding. I use the thing in manual mode set up as follows (with notes):

Tone Modify - Fat (see OD section). I don't really have any use for the other settings. The acoustic simulator is particularly hopeless with either of my guitars. I get closer to an acoustic tone in position 2 on my tele' through my clean channel.

Compressor - a little boosted over straight through and a bit of squish. Nice as a clean boost and for pushing the OD. Not a bad sounding compressor which is a relief as it lacks any fine control over the effect.

OD - I've several favourites here. For standalone use I like the Natural OD, very amp like and transparent. For OD pedal duties I'll use either the TS or OD-1 models with a slight preference for the OD-1. The Guv'nor model is great for Marshall-in-a-box tones and the RAT is, well, a RAT. The Distortion+ model gets you that US 70's tone. Crunch gets a bit of VOXiness going on.
I'm not that sold on the other models. The BD-2 and DS-1 are ok but I'm not convinced by the Fuzz Face and I've no use for a Big Muff or any of the other higher gain models. The bottom control (active bass cut/boost) is a masterstroke which extends the tonal range of any of the models beyond the usual treble cut tone control (hmm, a Tube Screamer with a bass boost, where have we heard that one before).
For use with my amp I'll set up a medium gain tone on the OD-1 model and use the Tone Modify and Compressor together for a fat boost. This gets me very close to what I had going with the FD2 I used before. I use my amp's OD for Marshall tones and can still push it with the OD-1 for higher gain. Lots of textures here without even saving patches. My backup/travel light rig is the amp and an SD-1.

Modulation - The chorus and tremolo are both fine. As luck would have it I get the sounds I want with the knobs in more or less the same position so switching from chorus to trem is just a matter of leaning down and twiddling the selector. The vibrato is a great model of the Boss CE-1/Roland JC120 vibrato, excellent for Shoot Out The Lights era Richard Thompson sounds with a bit of compression. I'm not a big user of phasing or flanging but they work. The rotary is ok but no match for the excellent rotary effect in a VOX Valvetronix amp (or a Leslie, but I'm not crazy enough to carry one around). The Harmoniser's quite fun, Big Country anybody? I find the Univibe very muddy but then I'm not a big Univibe user.

Delays - How did I live without tap tempo? I use the analogue setting for listening pleasure at home and the digital delay in a band setting. The digi delay just gives more presence and cut to the repeats and prevents that "where'd my tone go?" problem in a mix. Even cooler the tap tempo in digi delay mode is not bound by the range selector knob.

Reverb - Ah, now the bad stuff. This is not switchable. The spring model is horrible with no effective high end damping. The room model is OK and usable in a pinch. My amp has a great sounding Accutronics spring reverb. I use that.

The volume pedal and tuner work well enough though not as well as, say, the Ernie Ball VP and a Korg DT10 I was using before but they get the job done. I like the fact that the wah is switched on just like a Crybaby (toe down and switch). I don't use a lot of wah but it's there ready to go without hauling an extra pedal.

On the whole I'm very pleased with this. One cable in and one out, a power connection, the insert cable to the footswitch and a Boss footswitch for amp channel and I'm up and running. Plus it'll run on batteries to avoid power connections in the spilt beer zone, an 8 pack of AA's in the lead bag and I'm covered. I was mightily impressed with the build the switches, pedals and knobs are positive and the casing is rock solid sheet steel. The jacks are properly bolted to the case even if they're probably board mounted. The battery cover is the only flimsy item in the whole package. It fits nicely into a little padded zip-on lead bag I got with a Rockbag gigbag with all leads and switches.

For home and recording use the memories are handy for saving tones where the silences and the volume inconsistencies can be lived with in a no pressure situation.

Now the bad bit. The Behringer AB200 I bought as a footswitch is a serious POS. It's plastic and the casing obscures the jacks meaning you can't use right angleed jack if you wanted to use it as an A/B box. The switches themselves are decidedly moody. The only good part it that it's a (cheap) copy of the Boss switches so clips into a single unit with my Boss FS-5L channel switcher. I suspect that the Behringer casing will crack and fail connected to the aluminium casing of the Boss though. Saving NZ$20 on the Boss FS-6 was a mistake. I'll replace this as soon as funds allow hopefully before it breaks so I can get some money back on it.

The ME-50 has now been superseded by the ME-70 so there should be some good deals available. I'd recommend it for anyone who wants a lot of effects variation in a simple to operate unit bearing in mind my caveats above about the memories. As a "row of stompboxes" without the spaghetti it's hard to beat.