I was pleasantly surprised to find out it is free, and I didn't run into nearly as many issues with download time as a lot of other people seem to (even after switching to Orcon Unlimited yesterday - thanks Orcon!)...
It downloaded simultaneously on both of our MacBook Air's in about 90 minutes, and we also upgraded 2 iPads and 2 iPhones while Mavericks was on it's way....so not a bad use of bandwidth!
I like it a lot, it's continuing on the "refinement" path that Snow Leopard started down. Some of the new features are great - in fact I'm working on 2 displays now and the ability to change Spaces on each display separately is FANTASTIC!
I'm yet to dig too deeply into features but so far I'm liking it a lot. My MacBook Air (mid-2011) feels much more responsive in some of the apps I use daily (Office, Evernote, Safari/Chrome, Omnigraffle, etc), and I like the visibility over power usage on an application by application basis in the Battery applet.
What are your thoughts? Found anything cool?