I owned the AE212 and only sold it so I could pick up 2 AE112 cabs. I like being able to grab one and use it on smaller gigs, or 2 for bigger gigs. I have an AE210 on the way for medium gigs as well.
The AE212 does sound slightly different than the 2 AE112 cabs, but not very different.
This line of cabinets has completely killed my cab GAS, and I was a bit of a cab whore before I settled on them.
The very last production run of the AE112's used the 'revised crossover design/voicing' that was also changed in the final runs of the AE210, and from what I understand, results in two AE112's sounding a bit more like the AE212, although still a bit less low end extension.
The final version (vertical) of the AE210 sounds more like the AE212 (at least up top, not nearly as big down low) than like 'half an AE410'.
I too find the AE212 and the final voicing version of the AE210 to cover most of my needs, and have sold, or am selling, virtually every other cab I've owned (even my beloved AE410, that hasn't been out of the house in a year).

