This is the model I bought...
http://www.defender.com/product.jsp?path=-1|51|806|315133|823306&id=678987
I had the extra room so I went with the "household" bowl instead of the compact (probably not much difference in size, but...)
It uses 1-2 quarts per flush according to Jabsco. The water usage is easily controlled with the switches which are pretty straight forward to operate.
I tapped into the fresh water going to my sink under the cabinet. I cut in a Tee and added about two foot of hose to the solenoid which I screwed into the cabinet under the sink up high (needs to be several inches above the toilet). With numerous tries and a few four letter words, I was eventually able to route the provided water supply hose under the cabinet through the existing raw water entry to the back of the toilet. A new install or patching the old holes would be easier.
The other "fun" task was routing the wires. I learned a lot about how the wiring and paths/chases during this time. I mounted the switches near the ceiling centered behind the toilet (to protect them as much as possible when using the shower) and routed the wires to the solenoid and to the macerator motor on the back bottom of the toilet. I was able to route the wires along the discharge hose as it came through the wall. I needed about 20' of 12/2 marine cable.
I also needed several hose clamps (bought the high end ones to get a good clamping seal). The toilet came with an adapter for the existing large discharge hose. Oh, also needed a couple feet of the smaller discharge hose because I had to do a u-turn because of where mine exited.
Overall, I am very pleased with the install and would definitely recommend the conversion! I will snap some pictures and post them of the key pieces over the weekend.