I use a pair of subtronic alphas! They are the best guns i have had.
They are very powerful. And I have never had any TTL problems with either just one or both wired into my F100 housing. I use TTL for every film shot I take my subtronics & don't have a problem with exposures. There are many examples of shots taken with my subtronics alphas in thegalleries on my website. I also use them in manual only with my d100.
What I really like about them is they are strong and reliable. An hour charge on 110v or 240v in the evening and they last all day. And I take a lot of pictures (in the hope of fluking a good one). Their light is a bit warmer than my previous strobes - which is nice. Plus there are no batteries to cart around. plus the only O-ring to worry about is the flash-synch cord plug. I also like the metal finish. Looks much cooler than yellow or orange plastic on the diveboat!
Dislikes: the alphas are heavy in the water. It is hard to fit diffusers to their domed glass ports (I use white plastic bags or white cloth). They are also heavy in the luggage - can be a problem for SE Asia travel.
I usually shoot them as a pair, but in 2003 I started to shoot them quite a lot on their own. Very nice as a single strobe. But not really wide enough to cover a fisheye! The image below was taken with D100 + 10.5mm FE and you can see the circle of light that the single subtronic lit.

Alex