I'm kinda ashamed to admit this, but I'm currently running desktop Linux as my main OS. (This is somewhat accidental, what with the recent death of my newer, dual-booting box...I can explain further if you want to know.)
I'm less ashamed to admit that I'm a fan of Homestar Runner. Put the two together, and you can guess that I've tried to use Macromedia's Flash player for Linux. Emphasis on "tried."
The Linux Flash player is hideously buggy, and brings Firefox to a crashing halt on what feels like half the Flash ads in existence. This is an indictment of both Mozilla and Macromedia, but neither seems poised to change any time soon. To make it impossible for plugins to crash the browser would require a complete overhaul of the Firefox plugin model. And to fix the Flash player for Linux...well...
The above blog post explains why porting Flash to Linux--or, for that matter, anything besides 32-bit Windows--is so hopelessly complicated that it's a wonder the Linux release has ever seen the light of day. Mac OS X users should consider themselves extremely lucky.
Flash has the double-whammy of containing lots of optimized assembly code and being a multimedia application; the Macromedia legal team's insistence on avoiding any GPL or LGPL
application components makes things even harder. (GPL avoidance is obvious, but how exactly do you write a non-trivial Linux app that doesn't link to glibc? Which, I might add, ldd tells me that the Flash player does.)
Being the mere amateur coder/"egghead academician" that I am, I haven't really had much experience with code portability. Have the rest of you got any comments?