Here’s the short answer! :)
Hooking up an External HDD would fix the 1st, 2nd and 4th issue for sure. I suspect it would also resolve the 3rd issue to some degree (navigating 1080p files involves juggling a lot of data, there will always be a short pause before play resumes).
For the 1st issue (3 minutes to see network), after turning on the Live, don’t immediately try to navigate the network. Give it 30 seconds or so. I find that immediately accessing the Network Shares after boot-up causes the Live to not see the network and then it takes several minutes before it’ll work.
For the 2nd (network shares), you are the master of your own network and security settings. The Live can’t auto-magically decide what you do or don’t want shared. It is a pain sometimes but set aside an hour or two at the weekend for organising and sharing your media how you really want to. Once it’s done, it’s done and will no longer be an issue. ;)
For the 3rd point, I pretty much explained that in the short version. :)
Most of my media is 720p; I do own a 1080p plasma TV but until recently had limited storage so chose 720p (also, I use wireless-G and 720p streams better). It generally navigates quite quickly and resumes fast enough for me. 1080p should stream fine on Cat5 cable… I’d assume navigation would be quick too but as I already mentioned, it’s a LOT of data and there will always be a small lag before play resumes even in the best conditions.
For the final point… do you have a really slow computer? Or more likely, you’re trying to write to a HDD at the same time as you stream an HD movie. That’s asking a lot. If you have several HDDs in your PC (as I do), you can get around that problem by downloading to a different HDD than the one storing the movies you want to stream.
Or get that external HDD. :)