I installed a Champion 4 toilet in my house about 6 months ago.
When I set the toilet on the wax ring, I didn't notice it being particularly difficult, but I am not familiar with many other toilets and their relative weights. I had installed Kohler Wellworth lite 3.5 gal flush toilets about 15 years ago, and it was not much harder. My guess is that the Champion weighs more because of the 2 3/8" trapway - a good tradeoff in my opinion.
I had read about the recessed screws in the tank and someone posted to use a 1/2" deep socket. I tried this when installing the tank and it was simple and easy. I followed the directions to center the tank on the bowl and tighten the screws evenly and had absolutely no problems. The gasket that goes on it is incredibly thick and compresses a lot. I can see how it would be very difficult with the chintzy wrench they supply with the toilet.
I have been using the toilet for the last 6 months without a single clog. It has incredible flushing power and it amazes me every time I flush because is uses so little water and yet has so much force. In fact, I have lowered the water level on the Champion as low as it will go to conserve water. The toilet is also very quiet - the whole flush is over in a couple of seconds and the refilling of the tank is pretty quiet.
The toilet wash function works very good - it is a very shot duration intense whirlpool of water that effectively cleans the bowl. The everclean anti microbial surface probably helps in this regard also - water still beads on the surface after 6 months with no cleaning.
I installed AS Cadet 3s in my other two bathrooms. They are the one-piece, ADA height, 1.28 gallon, watersense, elongated version. They also have exceeded my expectations. I would rate the Champion as the better of the two models in raw power, but the Cadets have never clogged either. My water bill has been almost halved.
I have had no problems with the quality or reliability of any of my AS toilets (so far). If I have a flapper problem with the Cadet 3, I will take 5 minutes and replace it, but I honestly don't believe that it will be necessary.
The flush tower on the Champion 4 has been redesigned, and I am not expecting any problems with it either. It has a 10 year warranty that covers all parts of the toilet including the internal parts.
I installed a Toto S300 washlet seat on the Champion (it would not fit on the Cadet 3 one-piece toilets that I have.) In order to install this seat, the holes for the seat have to be exactly the right dimension or it will not install. It installed perfectly on my Cadet 3 and Champion toilets. I had to remove it from the Cadet 3 because the base of the seat just barely contacts the bevel in the ceramic that goes up to the tank.
All in all, I am absolutely thrilled with the performance, price and quality of the 4 American Standard toilets that I have installed, but the Champion 4 is my favorite by a small margin.