I'm a bit late to the party, but I own a 350 and love it. I love looking at boats of all kinds, but when it gets down to it, the 350 is the perfect boat for us right now. It has a bit of a different cabin layout than the conventional wrap-around saloon you see on many boats (like the 34 or 36). For us though, it's perfect--it's much more open down below, because there's less built-in "furniture". I'm surprised to hear someone above decry the handholds below---I think they're excellent; some of the best I've seen. There isn't a place in the cabin where I can't grab onto something solid (mostly overhead handrails).
I believe the 350 is the widest monohull you can buy (in terms of beam/length). Some people see that as a bad thing. I love it! I think it's great "living large". I look at a 380, or a 387, which is longer, but a foot narrower, and it just doesn't seem right to me. Yes, the beam could be a problem in a following sea, but that can be said for virtually any modern cruising hull design. The boat sails quite well (apparently even the folks at Catalina were surprised at this). It doesn't really take much wind to make it go, but I've been out in 25+ kts, and still felt fine. They biggest defect with the 350 is in the refrigeration system---they didn't put enough insulation in it, so it tends to be inefficient. However, this has been rectified in the Mark II model. If an inefficient refrigerator is the biggest shortcoming in a boat, it's a pretty good boat.
The 375 is an interesting boat as well. Actually, the differences between it and the 350 are so subtle that I wonder why they actually make both boats. It has one extra shelf in it, and a slightly better chart table. The main difference is that the extra shelf is a good place to a put a TV. Beyond that, it's tough to tell it's a different boat than the 350.
Catalina 350 "Golden Handcuffs" sailing out of Galveston Bay, TX