I have an ME-50B and like it.
PROS:
- It is easily the most user friendly MEU around, thanks to its many knobs that make tweaking easy, unlike most MEUs that have just a few buttons and many menus to scroll through anytime you want to adjust anything.
- It keeps your rig relatively neat and simple, as opposed to having a mess of cables and pedals hiding your floor, tripping you up and complicating your show setup.
- I like its different compressions, drives and flanger/phaser type effects.
- For a hacker like me, it's a lot cheaper than spending the bank on a truckload of individual pedals.
CONS:
- The filter effects aren't impressive to me.
- The tuner isn't very user friendly, and is definitely not stage friendly.
- As rnilson said, if you're just looking for a few certain effects, you're probably better off just looking at individual pedals, since individual pedals are usually superior to their digital MEU equivalents.