FarmerCharlie, my experience with an SLT-1554 wasn't great either, but despite that I went ahead and bought a Cub Cadet Commercial Z-Force S 60 a couple of weeks ago. It's the one with the black deck, Kohler Command, and ZT-3100 hydros. Fortunately it doesn't remind me of the SLT-1554 in any way except for the color.
I've only run it twice on my 2.5 acres so far to chop up some leaves left from the fall, but I'm completely impressed. I couldn't buy a regular ZTR because I have ditches that are forever muddy at the bottom, however I ran that Z-Force down them laterally with the tires just an inch from disaster at a pretty quick pace. There's an very secure feeling much like a lawn tractor, but it felt less likely to tip due to the track width and non-pivoting front axle so I didn't feel like I had to hang off the side like I did on my lawn tractor.
Seems well built and well assembled. I put a wrench or a screwdriver on every nut, screw, and bolt that I could get to and they're all secure. The belts are tracking true, the deck was adjusted perfectly even from side to side and there's an exact 1/4" front tilt. All the grease fittings were full.
The handling is excellent. The front axle does not pivot which is not as good for flotation, but as far as the ride goes it's kind of a wash. The front end does go up more if you hit a bump with one front wheel, but unlike a pivot axle it doesn't drop when one front wheel hits a dip. Of course it's more stable running across slopes because of the front corner support, whereas a pivoting axle is more like having just one wheel on the front, smack dab center. The steering is very light and easy compared to a lawn tractor and it performs zero turns beautifully. It only took me one or two quick turns to master the art of zero turning without leaving any damage, and that was on a soft and damp lawn.
Most surprising was the ride quality. My lawn is pretty bumpy and my SLT-1554 beat me to death, but I had no problem running full speed with this. The springs below the seat are huge and the seat is very well cushioned, and together they work very well.
Since it's so new to me I can't give you more than newbie impressions, but since you're looking at these I thought I'd go ahead and toss this out there. I really wanted a Hustler, but because of the ditches I couldn't do it. Now that I've had a chance to crawl all over this thing to examine it's design and engineering and have run it, I'm happy how this turned out and probably would have done the same for a flat lawn. It's nice to cruise around with one hand on the wheel. The 11 gauge deck is thinner than what you'll see on a Hustler, Skag, or Gravely, but I never had a problem with my old stamped deck because I don't mow lower than 3" and I don't set my rollers/scalp wheels so low that the deck bounces around. With good technique and care, I don't see why this deck won't hold up as long as the rest of the machine and since I have lawn soft spots and a drain field to mow, I can benefit from the lighter weight.