from my perspective
From my perspective, the way I use my Mac, I feel apple has done a nice job at incorporating nice looking features while also adding some time saving / management tools (like spaces). Spaces is awesome - I can have photoshop up on one, mail and safari on another, word (or pages) and keynote up on another, and something like DVD player on the fourth. This is great! will it slow down your computer though?
Although Time Machine is "sweet" (as SJ said many times), I would only end up using this feature a few times. How often do files magically disappear from your finder? For me, not many. This app reminds me of my initial feeling about automater. When automater was first announced, I thought "this program is amazing...i'm going to use it everyday." In reality, I've maybe used it twice my whole Tiger career.
The transparent menu bar is a good idea - assuming that Apple wants their computers to be "media hubs" for average people. Since I fall into this category, I like the idea of your personal photos, videos, and so on taking the main stage. The green grass photo is a poor choice on Apple's marketing team. It makes the transparent bar look pretty ugly, although if you were to have a nice ocean photo or something, it would look a lot much better.
I personally hate the new Doc. I'm not trying to complain about Apple, but for me, the doc is something I try to visit as infrequently as possible. What's the point in making it bulkier and more flashy? It is completely counterproductive to the transparent menu bar. Maybe they should have had a transparent doc to top it off

Well, hopefully it will still have its "hide" feature.
The new finder is great. And I personally love coverflow. It's such a great tool to flip through all your photos and see large thumbnails. Like I was saying, Apple is trying to market to college students and teens, so stuff like this does that. If you are a business person and don't like it, use a different mode...not a big deal.
Computer to computer sharing is awesome in the new finder...not that I use this much.
I thought it was embarrassing that Apple only made one new widget in the two or so years the dashboard has been out. Come on!...if they're so easy to make, why hasn't apple released a million new ones??
So, in conclusion, I think Apple was smart in having their fancy fun shinny additions to the OS system, but they also offered some solid time saving features (which happen to look nice at the same time). Next...a new version of iLife?? Anyone have any estimates about when this will be coming?