I upgraded from 10.8.5 to 10.9.3 a couple of weeks ago (on an early 2008 iMac with 4gb ram), and the boot times are
much faster.
I don't have to reboot nearly as much as I did in ML, but when I do, I'm surprised at how fast it loads, and that includes loading a number of startup items and extensions.
I ran a small app called EtreChek
http://www.macupdate.com/app/mac/48217/etrecheck
and it found a few launch daemons running that belonged to apps I didn't have any more. Once I got rid of those, everything sped up considerably.