I thought it's an issue because I don't normally see it; this behaviour stood out. And, it never did that on PR2. After hours, I did do the "backup, test/repair, restore" trick and now the cpu idles along at 2% like before and just like all my other 6.0 sites with similar numbers of users.
When it was pegged yesterday it took forever (or at least longer than normal) to access DB Programming, get voicemail email attachments, etc.