It's a fairly common strategy: buy a new computer, and then upgrade the RAM yourself. In general, it's cheaper, and often the new RAM is of better quality the OEM RAM. But Macs have been known to be picky about RAM, and right now it looks like if you want to upgrade your shiny new aluminum Macbook, you might want to wait: multiple crashing / freezing issues with third-party RAM have been reported on the Apple Support forum.
For example, this thread
is approaching 7,000 views at the time of this writing.
During various operations, including SuperDuper, downloading files and watching YouTube, the machine froze and I had to restart by holding down the power button.
Admittedly, this user was using Patriot RAM, not RAM from companies that pride themselves on Mac compatibility such as Corsair and OWC, but others have chimed in with similar problems in that thread and several others
that RAM from those two companies as well as Kingston are not immune from the issues.
The only sure-fire bet: Apple RAM, which appears to be Samsung-manufactured, BTW. Removing the third-party RAM and replacing the original RAM appears to fix the issues.
Theories are that the newness of the DDR3 spec is part of the issue. Right now, if you look through those forum threads, some get lucky with one manufacturer, while others do not. So it looks like the safest bet is either to wait for things to sort themselves out, or stick with Apple RAM.
Any readers having issues with third-party RAM in their brand new aluminum Macbook?