Just installed the new Release Candidate of Quantal onto a 10Gb hdd , Acer Aspire 3620 1.5GHz Celeron. The encryption went seamless from the install. The live USB release is still faster but Unity is more snappy than ever after processes settle after boot-up.
This is the first time I was able to get the (32bit) encrytion tool to work from Ubiquity (non-alternate).
A job well done by the Ubuntu dev team. They focused on some real bugs and pulled it off. Just awesome work.