MSN and Yahoo are quite 'specialized' given that they support video conferencing on Windows but not on the Mac. If you wanted to video conference with friends who have an MSN account, you're basically screwed on the Mac.
Though I agree there are more important applications (usually custom made apps for businesses), MSN and Yahoo aren't something to sniff at.
VPC is slow - I have been using it since version 3.0 though to get my windows work done (too bad it's too slow for games). Once the transition is complete though if apple buys it (or creates a better version) - it will be freakin' awesome! No need to reboot to play in the windows environment, run non-mac stuff at full speed WHILE running mac stuff on the mac side - ahhhhh geek heaven
I don't know why people think Microsoft would sell VPC to Apple. Microsoft is quite successful with VPC both for the Mac and for Windows (you can use VPC on Windows to "emulate" other versions of Windows or linux etc.). The question is how good MS will make VPC on the Mac once Macs use intel processors.
Why wait for this conversion? Just get a PC for your PC needs...they really don't cost that much. You'll get the speed you need, and any other specs you may drool over. I am getting one for games and other stuff, alongside my Mac. I think it is a good way to go.