The Mac OS App store. As a developer I feel this is horrible news. It's going to offer some additional form of promotion, however Apple is going to east 30% off the top and that's insanely higher than I'm paying right now. It's going to take away focus from developers' own sites, lower their direct sales, possibly limit or remove in-app automatic updates and compromise security on top of everything. The software protection used on iOS devices has been hacked and cracked to bits and I'm assuming the Mac OS variation Apple will use is gong to be the same or similar enough to get smashed wide open.
I can see it generally killing off the ability for developers to sell anything which isn't explicitly Apple approved. This includes fast updates as they need to be vetted by Apple before being pushed to the app store. When I used to use my iPod touch more often, I saw lots of apps which had an update but the authors were waiting for Apple to approve them which sometimes took a very long time.
Considering the iOS approval guidelines are vague in places and the approval process itself is completely opaque apart from a yes/no answer at the end, I don't see it being a good thing that Apple will have this much control over computer apps.
With regards to the OS, I always take everything with a HUGE grain of salt. Any mention of "lots of features" or "more than 300 features" I usually translate down to "less than half a dozen new features you'll actually notice or care about."
The massive "feature" list is just the usual Apple hyperbole. There are always some decent features in there but as you stated, most of them are completely useless or so minor that you wouldn't have cared if it hadn't made the release.