the standard 512MB should be fine for what u need. for as much as OS X likes extra RAM it is also much more efficient at handling what it has when compared to Windows XP. if u have the $ for the PB as well as the extra RAM, go for it. from what you've noted regarding your needs however, an iBook w/ a RAM upgrade might do you just fine as well.
also, don't get the RAM from apple, they overcharge thru the nose for their stuff. i'd go with a price search site like ramseeker or dealram to get a 512MB stick. if u r set on the 1GB, then i think newegg
has one of the best prices for PB RAM. it is not slated specifically for the PBs or the iBooks, but as you'll see in the reviews there are many happy PB and iB owners who have purchased it.