I think to some extent we should ALL be worrying about our IP :)
Good question though as its something I am keen to know more about (I currently do not obfuscate).
Having had some discussions with my manager at work, he said he doesn't obfuscate, but does NGEN on install, apparantly that should be enough to stop Reflector working on your assemblies, but I have no idea if this is true and to what extent, so please don't take it as gospel :)
Good question :) +1