I'd say you should try and get the transport for the extra X-Wing and pilots/cards. Maybe one more B-Wing so you can fly 3. Slave 1 is solid but I got the Lambda for thematic purposes and the cards (Advanced Sensors) as we setup 'theme' games for my kids and I to run through.
I got almost all of my stuff on eBay but really want a transport and am short the Imperial and Rebel aces (pre-release)
I forgot about the Lambda. I need to add that to my list. Also are the x wing cards that come in the transport good? I want the transport but don't see myself getting it for some time.