The Clip ZIp in fact is out in an 8GB version as well, in both black and gun metal gray color options.
As of last check, Amazon.com was discounting the price of at least some of the Clip Zip models. Even better, in my mind: through Sept. 6, SanDisk’s online store has all the Clip Zip models and colors at full retail price, but is throwing in free shipping as well as a free, nice carry case (retail price $15). Plus, register with SanDisk before buying and get 10% off your first purchase. All in all, a nice package deal at prices below or around Amazon.com’s (which doesn’t include the case). 
http://shop.sandisk.com/store?Action=DisplayHomePage&Env=BASE&Locale=en_US&SiteID=sdiskus
As to a comparison to the Clip+, I think you put your finger on the main differences. Having said that, and although I’m not an album-art-requiring sorta guy, it really is kind of nice, once you have it. Plus, with the Clip Zip, you also get a flush fit of the SD card (to help prevent rare issues with the card popping out), a stronger clip (altho the old one is pretty strong), a time-of-day indication on the what’s playing screen (it’s handy), a stopwatch (good for the gym, etc.), fast alphabet scrolling in lists, and some menu customizability.
You can read a number of professional and user reviews linked above at the top of the forum, to see if there are other things that people like (or not) in the new player.
One thing I also wonder: as the Clip Zip is new, SanDisk likely will be providing firmware upgrades for it in the next however long–bug fixes but also, possibly, enhancements. The Clip+ hasn’t received a firmware upgrade in a long while and unknown if any others will come, now, now that the new player is here.
Hope this helps; ah, choices!
