I am interesting in upgrading the harddrive (size-wise) in a 15" G4 Al Powerbook. (I currently have 80 GB). My Googling has led me to many sites that sell larger hard drives with instructions and/or installation kits/tools. Having never investigated these things, a couple of questions:  Anyone recommend a particular online vendor for this?  Are there any specifications I should look for (or avoid) when choosing a HD (like rotational speed, data transfer, etc) to ensure the new drive is fully compatible?  Other than getting more capacity, are there any other advantages of upgrading (such a performance or battery life?) Thanks!