From what I've read about hospital bags is that it makes it easier to know what you have, and quicker to find what you're looking for if you have separate bags for you and baby. I don't have any direct experience though.
It's my plan anyway. Bag for me for two or so nights and ditto for baby. If I need extras for an extended stay, my parents or DH can collect for me.
When are people getting theirs ready? I'm 26 weeks now. Still feels a bit early for me, think I'll have them ready for the end of July.