I'd be tempted. I'd like a cat, but I do have minor allergies to some cats. The worst I've ever had is a pair of Siamese that caused my nose to start running the moment I entered their house, others don't bother me unless they're sitting on my head and those itchy eyes/nose go away soon after the cat gets a few feet away, and some don't seem to bother me at all.
Unfortunately, I'd also have to convince OSVS,
George,
and Chinchilla
that getting a cat would be a good idea.
Jackie the kitty hasn't peed in the house since I posted this thread. I also have been more diligent about keeping the box clean, and we haven't left nylon things on the floor (daughter's play tunnel). That said, we still need to find a good home for her as my wifey still doesn't like her, and my 2 year old daughter has thoroughly entered the terrible two phase and terrorizes the cats. The other kitty handles it really well, but Jackie can't get out of Dodge fast enough.
Regarding the other pets, we took care of my nephew's guinea pig for a week. Jackie hardly acknowledged her presence, so I'd guess you'd be fine there. I'm not allergic to cats, so I have no idea if she'd really affect you or not.
Jeff