I would argue that simply encrypting the "sensitive" files leaves too much room for human error. Yes, the majority of crooks would not spend a lot of time looking for such material, but in the off chance they do, would you really want your entire business destroyed? Full disk encryption with a 20+ character password is the only way to go for laptops, in my opinion.

Also, if you're running windows, full disk encryption actually speeds up most tasks. On my linux box, boot time slowed down, but 200 MB random reads (typical for starting large applications) were actually only slightly slower:

  before: Timing buffered disk reads:  246 MB in  3.00 seconds =  86.24 MB/sec
  after:  Timing buffered disk reads:  246 MB in  3.00 seconds =  81.96 MB/sec