I'm definitely buying one as soon as I can find it. I have the whole series -- Mark I, II, and III -- and this looks like the best yet.
One major complaint I've had with all the Marks is the "holster-ripper" front sight. Years ago, there was an aftermarket replacement called the "Sport-Site" but it is no longer made. Ruger apparently realized that some people were not happy with this sight, and now offers what it calls a "Standard Front Sight" in its web store.
http://shopruger.com/Mark-IV-Mark-III-Standard-Front-Sight/productinfo/61018/
With the Mark IV, the loaded chamber indicator and the internal key lock are gone. That leaves the magazine disconnector as the last "lawyer-mandated" feature. We will figure out a way to remove it.
Regarding triggers, actually the stock trigger on the Mark I was pretty good. Not so much the triggers on the Marks II and III. I replaced those with Clark triggers. Apparently, the stock trigger on the Mark IV is acceptable. We shall see. I may or may not have to replace it.
The Weaver rail, which came included with the Mark III, is no longer part of the package. You have to buy it extra. Better yet, get the Picatinny rail.
http://shopruger.com/Mark-IV-Mark-III-22_45-Picatinny-Rail/productinfo/90623/
Incidentally, the orientation of the grip medallions is different on the Mark IV than on the Mark III. On the Mark III, they line up with the angle of the grip, whereas on the Mark IV, they are perpendicular to the bore. (It's little differences like this that really excite collectors.)