Same thing happened to me. Was around 90% complete and got the "service unavailable" message. I was on wifi so I thought maybe that had something to do with it. Manually checked for the update again and it downloaded with no problems. Actually... It downloaded even faster the second time.
Jelly Bean in Minnesota. Smooth download and installation with no issues. Phone noticeably faster and lots of new features. Thanks Google and thanks Verizon for a 'slow' and 'methodical' upgrade process.