Ergodox user here.
Bought my ergodox exactly a year ago from falbatech, and built it myself (i have never hold a soldering iron in my hands before that), which was great fun.
I'm using my ergodox at work, and carry it home whenever I need to type a lot.
I guess it's a personal preference but I just love the split design, I find it very comfortable. As far as I see it is a love or hate thing. Some ppl loves it like me, others don't find it useful at all.
The other thing I love in the ergodox is it's fully programmable nature, and that it's considerably easy to modify it further. I installed a trackpoint module in the right half of my ergodox. It's just plain fantastic, as I rarely lift my hand from the keyboard during typing.
For the problematic thumb cluster: I find the two 2unit high keys very easy and ergonomic to reach. But of course it depends on what key you map on them. I mapped 'e', backspace, enter and space there so I use them a lot. The other keys in the thumb sector is not so easy to reach, so I mapped keys there which are not used so often. PgUp, layer switch keys, alt.
All in all: after using the ergodox for a year now, every workday (and I am a software developer), I don't think that I'll ever revert to a non-split design for daily typing.
I can't recommend the ergodox as I see it's not for everybody. Conservative users don't like the split design idea, but who fancy it, it can be really really comfortable and effective.