Hi Guys,
Here is a shot of me using the Light & Motion BlueFin FX1 on a recent trip to Komodo. Maybe this will put the housing in context.

Sure, the housing is big, but I was surprised how easy it was to handle, in and out of the water.
The official specs from the LMI web site are:
Weight:
The dry weight of the Bluefin HD will vary with configuration. A standard configuration (flat port, no lights, no external monitor) will have a dry weight of 26 pounds. Dive ready weight including the camera is 33 pounds with a buoyancy just slightly negative in water. Fully loaded Pro Travel Package (UWA adapter, pro lights, and remote monitor) will have a dry weight of 44 pounds and a bouyancy just slightly negative in water.
Dimensions:
Length: Along the Housing base is 14.75 inches (37.5 cm). Optics will extend this a bit.
Height: Housing (no lights) is 9.5 inches (24.1 cm). Batteries will increase this to about 10.75 inches (27.3 cm). An external, top mounted monitor will increase this.
Width: Outside of the control handles is 13.5 inches (34.3 cm).
This is a system that has to be checked on an airplane. Period. There is no practical carry on option like there is for the TRV950 or HC1 housings. Those housings are really nice and small but if you want to shoot FX1 then you're going to have to live with checking the rig. I'm OK with that myself. I know there is always a risk of a missing bag, but it's a risk I take. Oh, and one could argue that it makes the system lighter than a HC1 system in a way. Have you tried to carry around a 30 - 35 pound carry on case with no wheels from one end of the airport to another along with your camera bag, laptop, and aching back? Carrying my housing with me just weighs me down. I checked the FX1 and since the case has wheels, I just rolled it out of the airport to the car. Much lighter (sort of).
In reality, traveling with the FX1 housing was easier than traveling with my still rig. The whole system packs into a custom cut Pelican 1620 case. I packed the housing, lights, monitor, 2 lenses, batteries, chargers, etc and was well under the 70lb weight limit. (ok, I know this a little vague but I am used to going overweight on every bag I check so to get everything I need in the case with weight to spare is rare for me)
Basically, everything but the camera, batteries, tapes were in the one Peli roller case. One (good or bad) thing about a custom cut foam case it that there is a special home for everything and it very well protected, but when every hole is filled, there is not much room left over to fill it to the weight limit. I hate to waste free baggage allowance.
Ok, so you asked how this compares to housings for the TRV950 or HC1. It is definitely bigger, but not so bad as to make you question the effort of lugging it around. In the water however, it handles much better than the smaller BlueFin.
The weights in the BlueFin FX1 can be adjusted so you can dial in the bouyancy. I tweaked it a bit to get it just the way I wanted it. The there are weights on each side of the housing that slide front and back so you can adjust the pitch a bit too.
Essentially, I made it dead neutral with a perfect level. Nice! In contrast, the smaller HC1 housing is a bit negatve and there is little you can do about it. I've never had a problem shooting it but some people have complained about it. If you switch from an HC1 to an FX1 you'll get a bigger housing, but a lighter weight and better balanced one.
If you look at the photo of me you'll see that I'm holding it with one hand with no effort. (reg in right hand) It was always like that. It was a dream in the water.
Of course the poor Indonesian crew members on my boat didn't like it very much. It took two of them to carry it from my camera station to the tender boat and back. That's why it has two handles on top. But for the record, I had no trouble carrying it anywhere myself. I never had to ask anyone for help :-)
Sorry to ramble on, but you asked for it. I've done two Indonesia trips with my FX1 housing now so I feel like I've got it dialed in and working for me. I can pack it all in one roller case, it's under the weight limit, and I have no problem checking it.
Dan