I have the M1 Abrams and although they may have changed to ESCs recently in the past they used mechanical speed controls. I equiped min with a Vantec ESC and it makes it much more drivable and reliable. The turret mechanics are a bit questionable and I have had to rework them a bit, I am very interested in that one pic showing some small flat motor driving the turret rotation rather than the cordless drill geartrain driving a 90deg gearhead that came in mine. I might have to give them a call.

To answer your questions, and my general thoughts...

Is it fast, not really, but two 250 Lb men can be pushed aside with little effort, it has insane tourqe.
Is it well built and does it need maintenance.... I can honestly say that as far as the end product goes, you are not getting your money's worth if it were a mass produced product. That is to say if the parts were flying off an automated line. What you are paying for is a fabricator's hourly labor, shop overhead, small quantity raw material and component ordering, and low production volume. In that respect, you are paying what it costs to make something like that. As far as quality goes; the main chassis and driveline is very solid, as is the top and turret. The barrel itself could support your weight. The bearings and roadwheels are definatly up to the job and even the small detail features like the grenade launchers and antenna mounts are made so tough they could be used as towing points. That is the good. The negatives are the track and turret mechanicals. The track is made from a very questionable alloy, too heavy and brittle to be pewter but not much tougher. The links are cast and then holes are drilled for the pins. Cracks develop along almost all the pin holes almost immediatly and some of the edges break apart. Had the links been machined instead of cast this wouldn't have been a problem. That said, my tracks have not broken or been thrown by any defects but I would rather all three links ina row be solid rather than one solid, one cracked and one missing. As heavy as the tank is, and the treads are 44Lbs each if I recall, breaking down the track and servicing it is a chore. As I said earlier, the turret's major components and pivot points are very tough. However the motors and drivetrains opperating them are weak and unreliable and almost seem like a last min. hack not on par with the rest of the tank. The barrel elevation is run by a small motor with a reduction gear, driving a brass ujoint like a tamiya driveshaft, turning a bevel gear, that mates with another gear that raises the barrel. There are no limit switches and the mechanism moves too fast. The turret rotation is run by what looks like a cordless drill drivetrain and a 90 deg gearhead, the mechanism also moves too fast and is not precise in it's stopping point.

All things considered it does have real shortcomings that can be dealt with but those things should have been dealt with in production. If you can put those things aside, or fix them, then by all means you will enjoy the tank.