The main problem that people face when bumping the timing is that it usually requires you to run 93+ octane fuel to avoid detonation. It does give a few horsepower and in some cases more than that. I like to run my car at 9-10* BTDC so I can run 87 octane fuel all year long. However if I decide I want the extra power it only takes five minutes to advance it to about 14* then fill up with 93 octane fuel and have fun.
I just set mine to 14* degrees, a nice medium from 10* and lower than 16*. I had 1/2 a tank of 87 octane in the tank and topped it off with 91 octane and have had no problems at all. There was a slight difference in power, all in all a good mod.