I have a 455 and 40 loader - it works very well. It's a big garden tractor though, not a utility tractor, so if you are buying it primarily for loader work I would get something bigger.
I don't remember the weight capacity exactly, but the loader is a little wimpy in stock form, due to the 1.5" boom cylinders. I upgraded mine to 2" and now I can lift plenty, although it moves more slowly, of course. The tractor only weighs about 1000 pounds, so even with plenty of
ballast, it does not make sense to try and lift too much. I may actually go back to the 1.5" cylinders at some point to gain back the lift speed.
One limitation of the 455 / 40 is that the 3 point and loader bucket cylinders are on the same hydraulic circuit, so something like using the loader with a box blade is a bit of a PITA. On the plus side, the loader goes on and off easily, and can be used without removing the mower deck. Also, the compact size is really, really nice when doing something like spreading mulch - you can squeeze right in around trees and bushes. When I'm not using the loader, I park between the loader arms, so it doesn't really take up much shed space.
The bottom line is that I am very happy with the setup for home use - spreading mulch, moving rocks and dirt and the like. It turned my spring chore of 18 yards of mulch from a 10 hour backbreaker into 2 hours of fun seat time. If I was going to be moving lots of dirt routinely,
I'd want something bigger.
Happy to answer any additional questions.
Tim