Not in the acting or celebrity sense - in the Saturday Night Live hosting sense.
Like everyone else, I love Alec Baldwin's performances as SNL's default host, but at some point he's bound to get tired of the job, and once that happens, they're going to need someone to act as a go-to guy for hosting duties, and they won't find anyone better for the job than Jon Hamm.
Having watched a few episodes of Mad Men, I knew of Hamm only as the taciturn one that women seemed to swoon over - an aspect of the show that SNL parodied with an incisiveness I didn't think their writers could manage these days. After his relevatory performance last Staurday Night, though, I'm suddenly a fan of the actor, and looking forward to whatever he'll do next.
These days, when most SNL hosts seem so incredibly uncomfortable with the very idea of performing comedy - let alone doing it live - Hamm displayed both great comedic timing and a facility with characters. Frankly, he made most of the cast look like amateurs on their own show. In his 28 years on the show, I've never seen Seth Meyers (TV's Smuggy Smugerson!) be anywhere near as funny as Hamm was doing a James Mason impression.
How great was Hamm? In an entirely solo sketch, centered around pitching a product based on his own name (Jon Hamm's John Ham: The Ham you eat on the toilet), he managed to salvage questionable jokes with impeccable delivery. To put this into perspective, a few years ago SNL did essentially the exact same sketch with Peter Sarsgaard (Get it? SARS Guards!) and it was two minutes of dead air. In sharp contrast, Hamm knocked it out of the park.
If there's a brain anywhere inside 30 Rock, SNL has just found a new perennial host, and I couldn't be happier.
(Sorry I couldn't provide videos - although they're supposedly available from NBC, for some reason they can't be searched or looked at it my country, so I've no way of hunting them down. Next time around I'll audiotape them)