I don't think it's great when you have your fingers. You can only see one thing at a time, anything ahead or behind is obscured. And there is also no way to navigate through anything in segments like there are with a scrollable list.
Sure, cool, you can see a preview of a document or w/e it is. 1) you can get a preview of the document with out cover flow and 2) seeing a little thumbnail of a research paper isn't as telling as a title because the thumbnail is too tiny to make any of the text out.
It's simply not practical. Sure you're buying into oh it looks cool, but that has nothing to do with practicality.
I've never seen anyone use cover flow when they were legitimately looking for a specific thing. EVER.
When coverflow came out for iTunes, I didn't see it as more than eye-candy either. I'm 21 and most of the music I own was purchased in digital format. It's not really helpful for navigation because I don't have any idea what most album art looks like or which albums contain what songs.
I was excited and thought I used coverflow quite productively when it was introduced into finder for documents, however. I try to keep everything in digital format. The most efficient way I could think of for converting my stacks of paper into PDFs was through a repetitive naming scheme that didn't help me much (i.e. - scan0001.pdf). Coverflow made it pretty easy to see a full-size preview of a document without opening it. I could then easily rename it to something more detailed (i.e. - 20090316_receipt_jewel-osco.pdf). It was also an extremely helpful tool for entering data in spreadsheets to determine if it was worth filing a Schedule A or tracking gas mileage.
In response to your biggest complaints:
For renaming files and data-entry, I think it's helpful to only allow one thing to be clearly seen. I'm not on a Mac now, so I can't check, but I don't recall the preview functionality being as quick before Coverflow. You can expand the size of the preview in finder quite easily. I was reading the data from my receipts and documents with no troubles.
On topic:
I'm in agreement with most here. I'll be glad to see the OS with a unified look. On top of being more comfortable to use, it should be easier to support with novice users. Very subtle differences tend to add lots of confusion and shake the user's confidence with their support person, especially with phone support:
"Click the blue 'OK' button"
"There is no blue 'OK' button"
"What are you seeing?"
"There are two gray buttons: 'Cancel' and 'OK'"
---------------------------
"...you can navigate your movies folder by clicking-and-holding the scroll bar"
"What's a scroll bar?"
"It's the shiny blue oval on the right side of the window"
"There is nothing like that here"
"Is there a flat gray oval?..."
