I've been playing with the new 2.7 RC1, and I'm very impressed. It's slick and fast and I really look forward to using it.
I am, however, disappointed in a few things. For one, why can I still not have subcategories for link categories? I wouldn't think this would be hard to implement (really, is it all that different from regular ol' categories?) so I'm confused as to why we don't have it.
Second, why are there no categories of any kind possible with the new Media library? I'd like to be able to segregate my images according to their intended usage.
Heck, maybe a frontpage widget where I could select a single or multiple categories to be displayed as thumbnails, not necessarily just showing everything under the sun would be nice as well, though I could see why that one might be better left as a plugin or extra widget.
On the whole I think it's a good revision and I look forward to the final version this thursday, but I thought I'd drop a couple words on the areas I feel could use some improvement. I hope it's clear I mean this as constructive criticism and not just a bunch of whining :)