Re: Pitfalls of trading up?
Single handling a 30ft wouldn't be a problem at all. I'm on a 32ft boat and she's a breeze to manage. Rolling furling helps, as does self tailing winches. Don't worry on that side of the issue. You may fret a bit over things at first but in no time she'll start to feel like something you can pretty easily man handle around.
Engine maintenance will go up. My current boat has a bear of an engine to get access to. But get something with good engine access and you should be able to do things yourself. CO2 detector is $10 at Walmart.
Rest of the stuff should be pretty similar to your 27ft boat. Winches a little larger, lines a little thicker, sails a little larger, but not terribly different. And if you plan on staying that size for the long term then you can really invest on good long term customization.
My current 32ft boat feels pretty spacious for me. Lots of storage and no complaints there. She's real comfortable. I just wanted to go to 37ft for a larger galley(I'm a cooking fiend) and a sort of 2nd mini cabin area for family staying over with me. I'm hoping that would be my final upgrade.