There's a very good, and detailed set of instructions in the tech section of Ruger Forums that will show you how to get the factory triggers re-worked for exellent service.
I've re-worked at least 150 77 MK IIs over the last few years(including 77/22s, 77/22 mags, and 77/Hornets). I usually will lighten them to about 2 lbs, and take out the creep, which, in my opinion makes them as good or better than most after market triggers. I have taken them down to around 1.5 lbs(safely), but in my opinion, 2 lbs is as low as any hunting rifle should be lightened.
Like S S said, it's most definately worth the time, and effort, but only try it if you're very familiar with triggers, and at least somewhat experienced in working on them.