Here's my usual advice for buying and selling anything that depreciates as quickly as a computer. It's worth more if you're selling and less if you're buying. What does this mean, beyond the fact that everyone is trying to get the best possible deal?
It's worth more if you're selling because, supposedly you'll need to replace it with something. That may (or in your case probably) may not represent an improvement in line with the cost of upgrading to a new machine.
To the buyer, it is worth less because there are new machines that are better, and waranteed available at similar cost. And since everything is depreciating anyway, good deals come to those who wait. If the buyer really needs a machine now, unless that Pismo can be had under 1000, I suggest an iBook. It's new, it's faster, it has more disc space, and a warantee. Unless you can get it very cheap, go for a new machine instead.
To the seller, Why do you want to get rid of your machine anyway? The new machines really don't do anything that your machine can't, or at least they can't do it so much better that it justifies the cost -- Not for someone who already has a perfectly capable machine. Unless you can get a really nice chunk of change for it, just keep it, it's quite good.
'Catch 22' anyone? Pismo: it isn't worth buying used, but it also isn't worth selling for any of the current machines. <img src="graemlins/hmmm.gif" border="0" alt="[Hmmm]" />