The blockchain is getting really big and it takes like a whole day now to download it. I think the size could become a problem in the future.
This was my biggest problem with bitcoin-qt -- and why I didn't get into it 6 months ago. It took days (literally) to complete, and never did. I finally gave up and figure this shit would never work.
Then someone told me about multibit a few months later...and I discovered coinbase. I have since stopped using coinbase, infavor of multibit.