Finder doesn't show thumbnail previews for RAW files
Raw support for cameras is something that changes with almost every OS update. Specifically, Lion 10.7.0 only supports some cameras, and 10.7.1 adds more, and so on. Also, according to this KB article on what cameras Apple supports - it is similarly vague that you need specific versions of Aperture or iPhoto to even see whether your machine needs a RAW camera support update.


http://support.apple.com/kb/HT4757


So, it looks like Apple is adding raw support to the OS in combination with you having a new enough version of either iPhoto or Aperture. I would say, you might want so jump to 10.8.3 and install the latest iPhoto from the Mac App store since my feeling is Lion intentionally changed RAW processing to exclude anything it wasn't sure it supported instead of 10.6's we'll try to draw anything and if it crashes, so be it attitude.

However, if you don't want to spend $40 on this, delay the upgrade to Mountain Lion and just buy the latest iPhoto (if needed). At that point you can call Apple support since you recently purchased iPhoto (or possible recently purchased Lion) and ask AppleCare to verify your camera model is compatible with your software versions. You get 90 days of complimentary software support anytime you purchase Apple hardware or software since they want you to get up and running with your new purchase.