Have a Samsung 840 SSD in a Thinkpad R60i running Xubuntu 13.04 /w 3GB usable RAM. Provisioned it with 20% free space and enabled TRIM, and it was fast as greased lightning to start, but four months later it takes three times longer to boot. Only down to 30% free in my ext3 file system and only installed 500MB of apps since install.
I have seen Slow Samsung 830 SSD! and did update the firmware before install.