This is fixed for the next build by making sure all the necessary postvars are there. Now if a second request occurs, the duplicate revision error would be triggered as originally intended.
#2 happened because the type of compression we are introducing in 2.5 for the revision table doesn't play well with mysql_ functions unless the compressed data is also encoded in the database.
The Web Developer toolbar has quick access to a number of settings allowing you to disable the cache or javascript, or view the response headers, or validate HTML, CSS, etc. There's a lot more it does as well but this is mainly the extent to which I use it.