Gianyar is a town that tourists don't visit often because it is an administrative centre but it's district includes some of Bali's main attractions.
The only thing in the town itself that I can really recommend is the night market which is quite impressive. It is very big and there are few tourists. The food is exquisite, although very spicy, and different from what you find in other places because it is not designed for tourists. I recommend you try babi guling (spit roasted pork), a Balinese specialty - it's a real treat!
The town doesn't have much accommodation. And that was what attracted me to the town, the absence of tourists.
And the town is also geographically well placed: 20 minutes from Ubud and the Bali Safari and Marine Park by scooter, or 30 minutes from the beach...