Good hammer users are the most valuable member in a party, aside from the god-like bowgunner. At least in vanilla Tri that was the case. I was never much of a hammer user myself, but it was a helluva good time. I much prefer the straightforward action of switch-axes, with the occasional cluster**** bombing.
Took out one of the final bosses from the chaos route in the neutral route. 'twas an interesting fight. I've unlocked a bunch of sidequests now that an entire city's opened up again, so I've gotta do those first before moving on.