For me, this is reason enough in and of itself to upgrade. I use LR at home, work, and on the road and having to carry around an external HD with all my photos is majorly annoying.
How well does it apply the changes once you get the full size image back in there? Is it exactly as previewed on the small image or are there some quirks?
The thing that I've always wanted most in LR is the quick selection tool that photoshop has, allowing you to apply changes to that selection. The graduated filter doesn't work in many scenarios (trees or building sticking up into the sky) and painting with the adjustment brush is cumbersome and feels like a throwback to 2001.
Is the only way to set these zones with an ellipsis or can you select non-perfect areas via a selection tool as well?
First, I haven't spent too much time with offline edit mode but as far as I understand, it just stores a list of instructions, which are replayed later. So far seems pretty accurate.
As far as zones, only ovals and circles, which is indeed a bit limiting, but better than before. It will at least preserve each zone selection, and you can go back later and apply different adjustments if needed.