I own both full and compact, I've got the F-Series collection then I've also got the '91 Toyota p/u. Trust me it is a bit of a change BUT the fuel savings is quite worth it IMHO...
Even aside from fuel savings...I've never owned a full-size, but I've driven them a bit, and in some settings, the size of my Ranger really comes in handy...I've parked it a lot of places where even an F-150 SB wouldn't have fit, or would have been a really tight fit.
Drive a full-size around for a few weeks, and the Ranger seems positively TINY inside, but it also handles like a sports car in comparison...