I own three Magic Stomps (two acoustic and one v II eggplant), two DG Stomps, and an AG Stomp. Just missing the UG Stomp but those are still very expensive on ebay. Some things I have learned...
On my pedal board I use one MS last in the chain for amp modeling (since I go right to the PA) and another for reverb, or other miscellaneous modulations. I keep the eggplant MS near the computer (and old PC laptop which i just keep around as a front end for the MS), for editting patches and recording. There is a freeware patch organizer program for PC available at the yahoo groups (magicstomp and magicstomppro) that is helpful in maintaining groups of patches.
When I am playing electric guitar and traveling light I just take a DG Stomp. It is *MUCH* more tweakable on the fly than the MS (many chicken head knobs). I would never try to do deep editting live on the MS. If I am just playing acoustic, the AG Stomp is a great pre-amp/chorus/delay/reverb/mic-modeling unit.
All of the guts of the DG, AG, and UG stomps are inside the Magic Stomp. Just harder to get at the controls.
The Acoustic and Bass Magicstomps are identical to the version II eggplant MS, except for the preloaded patches. You do not need to flash the ROM in those, they should already have the latest version of the firmware (1.2 I believe). If you want the factory patches, you can download them from the Yahoo groups (or other places) and install without flashing the ROM. (Something that always makes me nervous).
If you have the original version 1 eggplant MS (without a headphone jack) you can flash its ROM to make it exactly the same as the latest version, including automatic feedback controls like the AG.
I love the clean fender amp tones I get out of the amp modeler into the PA at church.
The MS's can suffer from a common failure in an output transistor. The purpose of the transistor is just to mute the pops you get when the unit turns on, but when they fail they can put a +5v bias on the output signal. An easy fix is to just remove the offending transistor from the circuit. There are detailed instructions here
http://groups.yahoo.com/group/magicstomppro/message/928 .
Yes the input power is unusual. 12v AC. I just purchased my second DG from ebay and plugged it in using the power supply that came with it without looking closely at the power supply first. The seller had put a 12v DC adapter in the box by mistake. The DG did not like the DC power. I was in a dark room when I was trying this, and so didn't notice the problem until I got home. When I plugged in the correct 12v AC, it worked fine..... so far. It did start making some noise after about an hour of use. I will have to run more tests. If you are buying one make sure to ask if the unit has been audio tested, not just plugged in and turned on to see that the lights work.
Join the yahoo groups. They are not very active, but there are lots of good patches saved there.
-bhh