Bugger off, Winamp. No, really, bugger off. If I wanted a new version, I'd go look for it. The simple fact is, all I want is a program that plays my mp3's, and manages my playlist. If I wanted anything more, if I wanted bells, whistles, minibrowsers and related shite, I'd go looking for them.
Software reaches a certain stage where it does everything a reasonable person wants it to do. After that, any upgrades are just dancing paperclips and changing file formats to force people to upgrade. This is why Microsoft wants you to rent their applications now instead of buying them - people are starting to realise that Office '95 does everything that Office XP does, just with a different colour scheme and an incompatible .doc file.
Of course, if you're making software, the last thing you want is for people to stop upgrading, even if the software is free. Stagnation is death and redundancy. So you do stupid things like nagging perfectly content users into trying your new version.
Well, it's only so long, only so many repetitions of that popup window before the annoyance exceeds my inertia, and I go looking for something that won't tell me off for not keeping up with the Joneses..
(Some thoughts in this entry stolen from Joel Spolsky)