RC2 of 2014, clean install (really good clean-out after Avast's tool and reboot) was fast. Went to RC3 and the slowness appeared, with a spreadsheet in Calc taking about 25s to open first time and about 15s after. With File Shield off, it opened in 11s first time and 7s after.
Apps launched from Quick Launch bar always had a 2s delay; from the Desktop icons there was the same.
Cleared out all of Avast again, installed 2014 Final - same problems.
(BTW, was using Private Firewall).
Another clear-out, installed Comodo AV and FW. I takes a another 100MB of RAM but I have 2GB.
Calc now opens in 11s, no delays with icons, shuts down about 3 - 5s quicker (OK, only form 14s to 9s, no big deal).
Most notable is QuiteRSS - it was about 10 - 12s with Avast and is not 3s!
If this is fixed, I'd still like to use Avast as AV, as I prefer 'no, you can't come in' over Comodo's 'you're in but you may not do anything' approach.