I dormant / frost seeded a small piece last fall, overall things look good this year. The general feedback I hear is that dormant seeding is better for forbs than grasses in the first year or two as most forbs require stratification to break their seed coat.
Some say that grass seed maybe slightly affected negatively due the fact that most grass seeds do not have a hard coat to protect them through the winter, many people say to increase grass seeding rates to counteract this affect.
If you are going to dormant seed this year you should have killed off most of the competition already with a herbicide, depending where you are located you might still have some time left to do this.