Lobster, steamed Saturday afternoon, eaten Monday night? Pretty much what it sounds like.  1.25 pound whole Maine lobster cooked mid-day on Saturday and refrigerated until Monday evening.  Still in the shell, claws, tail, and all.  Still good?

I normally assume proteins will hold for 3-4 days, but I'm not as trusting with fish as meats, and I'm even more suspicious of shellfish.  Is that hunch justified?
According to stilltasty.com two days is the max, so you'll be fine as long as you refrigerated it within two hours of cooking.

Other sources claim durations of 4-5 days. As sarge suggests, use your nose.

Other sources:


http://www.lobsterhelp.com/lobster-facts.html
http://www.fao.org/wairdocs/tan/x5887e/x5887e01.htm