I, too, have heard rumors of problems with the Mark IIIs. I'd avoid it for now, as there are still plenty of new Mark IIs on the shelves. Don't mind all the hype in the gun magazines about the new Mark IIIs. Ruger is a big advertiser, so it's no shock that the gun rags all love the Mark III.
As someone else mentioned, make sure you get what YOU want. Handle as many different configurations as you can and pick the one that feels best. Still, you may later find that the one you buy isn't as great as you'd have liked it to be once you've shot it a lot. Don't be afraid to sell or trade once you get a better handle on your preferences.
Personally, I've had the Mark II Government Target model and a Mark II 22/45. The Government turned out to be too muzzle-heavy, even though I liked it at the time I bought it. The 22/45 felt better and shot as good as the Government, but the Zytel grip was never impressive to me. I'm shifting to the Buckmark, so I'll see how I like those. Before getting too enamored with the Rugers, I'd suggest you shop the competition, too. There are many variations of the .22 semiauto. Some are good and some are bad, but it's mostly in the eye (hand) of the beholder (shooter).