I used to have a CPE, which I upgraded to a CPP. I used /use them for developing mostly B&W, some E-6, in 35mm, 120 and 4x5 - mostly 4x5.
Capacities:
4x5
In one batch you can do 12 sheets with the CPE, or 18 with the CPP/CPA
120/220
You can do 3 spools with the CPE, or 5 with the CPP/CPA - one spool will hold one 220 roll or 2 120 rolls, although I found it a PITA to get two 120 rolls on one spool so I didn't do that.
35mm
CPE handles 5 rolls, CPP/CPA will handle 8.
Jobo offer 'Expert Drums' for sheet film which will work in the CPP/CPA but not the CPE - the Expert drums apparantly offer better consistency although I have had no problems with the 2509 reels for 4x5, and they will allow you to develop larger sheet film if you get into 5x7 or 8x10.
Generic things about all of them:
The basic principle is to use a small amount of chemistry in a constantly moving drum. This has advantages and disadvantages over other techniques - the biggest advantage is much less chemistry usage per roll/sheet. Since I like to use a lot of my stuff one-shot, this is nice. A disadvantage is that the constant agitation will oxidize rapidly those developers which tend to oxidize - I had to play for quite a bit to get Pyro to work well in the Jobo. Another thing is that when working with very dilute developers like Pyro or some HC-110 concentrations you have to watch that you have enough chemical to not exhaust your developer when using it one shot.
I use the lift, and find it very handy to get the timing accurate - I would highly reccomend the lift on any Jobo that you end up with.
The CPE and CPA have a single analog knob to set the temperature of the bath - I found that the calibration on mine was not right, so I always had a thermometer in the water bath and would tweak the knob until I got it to the temp that I wanted. Once tweaked, the temp was very stable.
The CPP that I have now has a digital temperature set - you dial in the temperature that you want and it is very accurate and very stable. I think that I get better/more consistent results on E-6 with this than I did with the CPE.