Well, much improvement, but not solved in my opinion.
I'm running Windows 7 (32 bit) with latest itunes as my headless media hub, with following connected:
2 x iPhone 4S, iPhone 4, iphone 3GS, ipad v2, ipad v1, 2 x ATV 2nd gen, ATV 3rd gen, 2 x MacBooks with itunes, and 2 x Window 7 PC's with itunes. ALL the latest versions. 50,000 plus songs, and 500 movies. So, a reasonable test bed for all that apple should be able to deliver to a connected home/family setup. My wife is very, very patient fortunately.
I've turned off IPV6 months ago - with great results - homeshares actually work now without dropouts.
I've also turned off general sharing - only got homesharing on - again improved connection times and some removal of oddness
However, the well documented popups nightmare took me VERY close to giving up Apple religion. Fortunately the latest Itunes release spared me from a costly trip to a Sonos supplier and the various Video server options.
But - the pop ups aren't totally gone. Can't tie it down, but days can go by with none, then suddently I get a hundred (which with a headless media server means everything still jams up). Well done - some have been consolidated to a little warning icon next to the Device to show that something didn't work again, but otherwise I get the same old 100 x "can't detect" or "can't find". Only fix - restart iTunes, all is well for a while.
Also, perhaps related, perhaps not, but probably due to the size of the libraries, when trying to use shared libraries on the iOS devices, it ends up with huge delays, and almost always a hang (with a half moon) or simply a blank library.
Apple just doesn't test their stuff.
Apple - if you're listening - I'm not a tech idiot - certainly way more capable that almost all of your target consumers, I'm a Apple advocate, that not only spend thousands on Apple, but influence others to spend thousands on Apple.
I've written this note after testing every possible scenario everyway I can, I've dissected every blog - the stuff just doesn't work that well. Please fix before my wife totally loses it, and I've got to buy some Sonos stuff.