Disc swapping is not a problem for me or you. But it is a problem for developers needing to figure out how to design the game around the size limitations. The game has to be split up, and quite a lot of data needs to be repeated on each disk further limiting what part of the disk can be used for new content.
To make it all fit you get heavier compression on fmv, compressed sound, fewer language tracks, no extras such as storyboards and making of videos like we used to get with games. If you're just pressing one disk, you can add all you want until it's full for no extra cost, hence the extras with uncharted and ratchet and clank for example. I think it's more fun to unlock a making of video after completing the game then to get an achievement or trophy.
But it's not all bad, all the more reason to keep some content out and sell it as dlc later.
Personally I hate disc swapping for blu-ray movies. I never watch any extras if they're on a separate disk. Not because of the effort of swapping, but they always make you watch all the warnings and other crap again before you are even allowed to get to the menu. Just be glad games are not that annoying (yet)