I found that detaching the metal plate and adjustable seat supplied with the Ultra, and instead using a Therm-a-Rest air cushion ($10 from Campmor) held in place with heavy duty Velcro, saves weight and for me is more comfortable. However, my wife finds the original seat more comfortable. Another option would be to use the supplied seat but use heavy duty Velcro and attach the seat directly to the large plastic piece that holds the seat, skipping the metal plate that goes under the padded seat.
The Ultra came with Kenda tires that inflate to 65 psi. I replaced the rear 20 inch (406) tires with Comp Pools (90 psi) and put Hookworms on front. I never used the emergency brake, so I detached it. But this is not recommended and I don't recommend it to you. Replacing the seat with the air cushion and detaching the emergency brake saved me about 11 pounds. The Ultra no longer feels heavy to me, although at first it did. I estimate the Ultra weighs between 60 and 70 pounds, which sounds heavy to a cyclist. When I first got the Ultra I was considering "souping it up" by replacing some parts with aluminum. After more use I decided that I like it just as it is.
You will probably want to shorten the cable housings a little, trim the brake cables with cable cutters, and lubricate the brake cables before reinstalling them. The design is simple and it is obvious how to adjust the tension of the heavy duty chain, which is used to drive the rear wheel. By keeping the chain under a little tension, you are engaged at all times while pulling or pushing. Maintenance consists of occasionally tightening the chain a little, putting a few drops of oil on the moving parts from time to time, and the usual wheel maintenance of tightening any spokes that become loose and keeping the tire pressures at the recommended levels.
If you get an Ultra, it arrives mostly assembled. It comes with instructions. You will need a 5/32 and 3/16 inch allen (hex) wrench, an adjustable wrench, and perhaps a C-clamp for squeezing the U-shaped part of the lever together when doing the final assembly.