This is a huge thread, so I apologize for not reading it all, but as I'm sure others have probably already mentioned, iTunes 8 has some notable bugs in it.
If you attempt to download multiple tv shows at the same time, using the 'simultaneous downloads allowed' option, iTunes 8 may very well freeze the entire computer or at least when using Mac OS X Tiger. I've read elsewhere of others having this problem as well. The problem goes away if you switch to NOT allow simultaneous downloads. This is a major bug, though that needs fixed, IMO.
Like others, I've attempted to download free HD tv shows. iTunes 8 will not download the HD versions if you have the "shopping cart" method selected for iTunes. I had it selected so I don't accidentally buy items from the iTunes store and so I can reconsider after I'm done shopping. iTunes will only download the standard definition programming with this method. There is no point in having a shopping cart option if it doesn't work right so this one needs fixing.
Once I switched to one-click shopping, iTunes 8 then proceeded to download the HD version, but I could also see that it was downloading a standard definition version as well. Personally, I think this should be a user option as some of us may not want the standard version taking up hard drive space and downloading time. But that's a minor quibble. The real problem is that iTunes 8 has a tendency to WRITE OVER or erase the HD version with the SD version that downloads afterwards. iTunes 8 then lists the HD version as missing its file. From what I've read elsewhere, this problem only occurs with SOME tv shows, but that's a nasty bug. The only way I could avoid that happening was to manually force the standard definition version to not download by selecting 'delete' from the "Edit" menu above while in the download area (right clicks do nothing in downloads).
I would really like to see an option for TV Show RENTALS at a lower price point as I have NO desire to keep or store television shows on my system. I typically watch a tv show once in a lifetime. They do not have the same 'repeat' value as music. I'm more likely to watch a movie more than once than a tv show, yet we have movie rental options, not but not tv rental options. $3 is out of line to watch a show ONCE, IMO, and yet the ability to rent a tv show I might have missed on cable would be invaluable, let alone the options you could have to ditch cable or satellite if you could rent cable tv shows. $1 seems reasonable to rent a tv show to me, maybe $1.50 for HD (I only really want HD, though).
AppleTV needs an update so it can order HD tv shows (and again preferably rentals). I mean it's called Apple *TV* which you would think means it's designed to watch tv shows. TV rentals for AppleTV ONLY even would be nice even. I use it to rent HD movies a lot. I never rent SD movies or buy tv shows with it. Apple could certainly get a lot more money from me if they'd rent HD tv shows to me for half the price of buying them. A subscription option would be even BETTER (i.e. $25 a month to watch unlimited HD tv shows or something like that; the same would be nice for movies as well and would be a nice alternative to Netflix at that point). ATV also badly needs a visualizer option as an alternative to photo slideshows while listening to music. That would be awesome on my 93" screen. The main thing that bugs me about the lack of an update so far is that Apple has been silent on if/when it will get an update. "Coming Soon" would be better than nothing.
It'd also be nice to know why certain movies are no longer available to rent. For example, Superbad is in the lists of Must-See HD rentals in AppleTV, but if you go to Superbad, it's only available for purchase in standard definition. There are no rentals period for it anymore either from AppleTV or iTunes so why is it shown under must-see HD rentals? It's absurd. I've read on some other sites that entire movies have disappeared from iTunes with no explanations given. What good is a rental service if they're losing movies instead of gaining them?