It's not fun if you're a user. Every developer of packages is the user of a much, *much* greater number of packages.
I'm a relatively long time user of free software desktops, and I have to say the regular breakage due to rewrites isn't fun. Indeed, my anecdotal view of things, based on other people in my local LUG who've been around quite a while, is that this breakage of important existing functionality (sometimes for little to no functional gain) is driving users away from Free Software desktops (typically to OS-X).
It's kind of a tragedy of the interests of the individual hacker over that of the community. While the individual hacker obviously feels much happier working on new and exciting code, the community at large and over time suffers from the fact the system never converges on stability (0.8 followed by 0.8, just buggy in different ways, as per JWZ).