Starting to feel tempted.
IFTI, I also have the Apple TV (160gb version).
Could I connect via wifi with the iPad2 to the Apple TV to watch a movie without having to have my MacBook (where the iTunes Library is stored) booted up.
Yes.
Slightly complicated though. To view a movie from the iPad via airplay through the Apple TV it has to be in a MP4 or M4V format (basically a format Apple support). If you can play it natively on the iPad you will be able to airplay it across to the Apple TV fine.
If its in any other format you need an app on your iPad that can firstly play the movie. With iOS5 coming along you will be able to mirror the iPad to the Apple TV, and watch anything you like, no matter what format.
For example,
I have a NAS, which I have set up as a DLNA server as well.
I use an app called 'Air Player' on my iPad2 and iPhone4 to connect ditrectly to my NAS and watch any movie I like, regardless of format (DivX, Xvid included!).
If the movie Im playing from the NAS to the iPad/iPhone is a MP4 or M4V format movie it plays using Quicktime on the iPad/iPhone. I can then hit the airplay button and watch it on my Apple TV2 in full HD (720p). Plays beautifully.
If the movie is in any other format, such as DivX for example, then I can watch it on my iPad/iPhone directly for now, but cant airplay it to the Apple TV2. However, iOS5 is due out soon which supports mirroring whatever is on the iPad screen to the Apple TV - so I understand that you will be able to watch whatever you want on a larger screen no matter what format etc - as long as it plays on the iPad.
My whole reason for doing this is that I wanted to be able to watch content from my NAS directly on my TV without having to have a computer/laptop on in between. This way I only have my iPad or iPhone on in between, which I much rather prefer over my MacBook. The amount of battery used to watch an entire movie is only around 2% since once you airplay the movie across to the Apple TV2 you can hit the sleep button on the iPad and it will continue to play, or you can continue to do other stuff on the iPad and it will still continue. Hence I can stick a movie on for the kids, and still use my iPad to sit with them and browse the net or get on with my own stuff etc.
You can play Music and view photos etc in the same way - but no issues with formats etc as they'll just work straight away.
Hope that explains it!