Sounds like the 512MB of include RAM isn’t enough—should I custom-order a MacBook with more RAM?
We wouldn’t use a Mac with 512MB of RAM, so take that as a strong recommendation to upgrade. Apple usually charges a lot more for RAM than you can buy it for by searching a site such as Ramseeker. In the case of the upgrade to 1GB, however, Apple’s prices are pretty much in line with the industry. If that’s all you need, it’s probably best to let Apple do it. But if you want a MacBook stocked with 2GB of RAM, you could save as much as $300 by ordering your system with the stock 512MB, pulling those RAM modules out, and replacing it with modules you bought elsewhere.