Also of note is 1.80 allows support of PS One games. I haven't tried it yet myself,
For me, the one of the big things of 1.80 is that it seems to fix the video pause sleep feature that was missing since the Vita launched. Specifically, if you paused a video, the Vita never goes into sleep mode. it would leave the screen on forever-- or presumably until the battery died. (But what it if was plugged in?) That's really bad... but now, it does seem to go into sleep mode, the screen turns off after 5 minutes? A welcome fix, for sure.
The big issue that is NOT advertised is that update 1.80 locks memory cards to a single PSN account. Some people have multiple accounts to access other region games, and this makes it harder to do. [Wired article]
And I'm sure that there are a bunch of piracy and homebrew blocks embedded in 1.80 as well.
Full list of features & info: http://blog.us.playstation.com/2012/08/14/psone-classics-coming-to-ps-vita-via-the-latest-system-software-update-v1-80/