I'm a firm believer in having as much RAM as possible, both for the present and for the future, as software requirements tend to change as new versions come out and most generally more RAM is needed. Been through that over the years with various Windoze machines. When I bought my iMac, before I even left the store I had Apple install more RAM to max out the memory, and then when I ordered my PB BTO I again maxed out the RAM. Yes, it cost me more to have Apple do it, but in the first instance because it was my first Mac I was a bit uncertain about opening it up and monkeying with the innards, and in the second instance because this was a new revision of the PB the Apple store didn't yet have the right memory chips for it. I was ordering BTO in order to get the 7200 rpm hard drive, so had the RAM added right then and there. Probably the next time I buy a Mac I'll save myself a bit of money on the RAM and order memory chips from a source other than Apple and stick it in myself.
A friend just got a second-hand computer and when I was setting it up for her right away we realized that the amount of RAM in it -- 512 MB -- was barely adequate, especially when we installed AOL v. 9 (Ugh. Eventually the family will be going to DSL and a "real" ISP, but in the meantime.... AOL it is. Yuck! Wow, is that software a memory hog! Between XP and AOL, there's not a lot of extra RAM space). So last night I went over to Microcenter and picked up another 512 MB RAM; on Sunday will be opening up the box and sticking that in for her... and here I thought my days of tinkering with Windoze machines were over!
OTB