Just bought one of these.
Basically it's awesome
The range of sounds is incredible and half an hour with the manual and the unit and it's actually quite intuitive.
I've seen some criticism on this board about the distortion (the Pod being better). I can't really comment as I've not used a Pod but I once bought a Line 6 Spider which I thought was a heap of poo. Nasty thin sounds and for a 60 watt amp it was unusable live due to a lack of power. I returned it and got a George Dennis Blue which was about 10 times heavier but is an excellent piece of kit, apologies I digress.
The comments about distortion misses the point somewhat as this unit is not just about distortion. The delays, chorus, reverb and other "special" effects are superb. I'm sure I won't get anywhere near exploring the full range of possible sounds that can be created (and used straight from the box) but I'll give it a good go!
You can look up the specs for yourself here
(check out the interactive tour) but in short -
Preset sounds - 50 banks with 4 sounds per bank. Accessed by 2 pedals to select the bank (up and down) and 4 pedals to select the individual sound.
User sounds - 35 banks of 4 sounds per bank available
Expression pedal assignable to various parameters (volume, wah etc.)
A "CTL" pedal that can also be assigned to certain functions such as to switch the tuner on/off or a great "solo" function that boosts the sound for a solo.
I paid £300 at the "real" shop associated with this
All in all a recommended Multi FX that is going to create practically any sound you want (including some rather excellent guitar synths).
Downsides? A lot of planning is required for live use (as it is with most pedals anyway). You've got so much available to you that you really need to write down what banks and effects you're going to use and try and plan them around your songs so you don't have to be going up and down bank after bank to get your sounds.
Also, the box is so versatile it's quite intimidating if all you want is a simple "stomp box" effects unit. As I'll mostly be using it for recording it doesn't bother me too much as I'd rather have too much than too little.