Wow, that Crucial price really jumped. I got an OWC 1 GB DDR for my new 12" PB on tuesday ($359). I went with OWC even though Crucial was slightly cheaper at the time because I have had good service from them before and I like the idea of using Samsung DIMMs like Apple OEM. OWC prices are usually pretty competitive (within 5-10% of the cheapest). I would suggest going for it - you will not find a much better deal in the present climate.
Jon