The 575s were short lived due to bad image and reportedly higher-than-normal incidence of crank problems. I never owned one so I cannot speak to the matter. The fact that it was replaced with a "cleaned up" 576 after just a few years would indicate that consumers and perhaps even husqvarna did not think highly of the saw.
I think generally when you get a good one, they're good. When you get a problematic one, they're problematic. They seem to come in both varieties. It's a bit risky on a used saw. If it's well used, congrats, it presumably stood up, but you never know if someone is unloading a well used saw because of problems...
The fact that it's been walkerized is a +/- depending on your outlook. Presumably it has more power as a result of the porting they did. I'm not too familiar with the ports or degree to which the walker ship pushes things, but all porting work is on a gradient, and I dont think it's too controversial to say that the more they chop the shorter the saw will live.