I think it's very nice from Blizzard to do this new patch, specialy in this way. They are a mighty company, and they have built it all on 3 game franchises: Diablo, Starcraft and Warcraft. So why not support one of their 3 most successfull franchise names while they are building a new version behind the curtains?
Btw, there is one other such example, and from a way smaller company (which indeed has much less resources than Blizzard): Worms. They were released in 1999. and still get official patches quite regulary. Oh, if only more games were like this.
Anyway, I went through some of the 1000+ comments that have already built up on Blizzard forums. And most are both easy to do, and logical. First off, larger stash and easier management of the stash. Like you guys said, it's a "treasure-hunt" game, with way too many things to collect, and no way to collect it all. Other suggestion was an ability to redefine your characters specs, by "moving" points from one skill to another; and another well needed thing I should say, as people don't want to replay whole game 10x just to get their character build "perfect". Third thing was to offer higher resolutions, and widescreen support. Shouldn't be hard to do it, and again, this is a very needed change as technology went way beside 800x600 resolutions. And than there are ofcourse bugfixes and stuff.
But is any of these things a bad point for a game, even for a 10y old game? Nope. People play it, my wife plays it a lot, and I guess a lot of people will be made happy with those several changes.
So i'm all for it, and I just hope it won't take a year or two to do it