The Driveway Guy crew sealed our asphalt drive. They offer a free in-person estimate, clean the driveway before and remove weeds along the edge, use an industrial blower to remove debris before starting, use boards to block over-spray (these may leave a black edge on the grass), used a trailer-mounted spray system and a good quality sealer. It was a very efficient crew and they were done in 30min. You need to avoid driving on it for 48hrs - and they provide the tape barrier at the bottom of the drive. Our driveway is about 17 years old and I am very happy with the even finish and the added protection a regularly applied seal provides. Sealers act like a thin shield for the asphalt composite; slowing the breakdown and making it more impervious to the weather and chemicals/soaps etc that get used on it - extending the life of a driveway with regular applications. DIY would have cost the same with all the equipment I'd buy... and the store-stuff is a thinner and less durable solution. I took 3 estimates and there was a range - but all companies say that the seal lasts 2-3 years before you need to have it re-done. I paid $100 last time to a door-to-door guy who knew his stuff and he did a good job, but the finish/coverage was not as good as this trailer-mounted 2-man operation.
Only negatives are the shiny look of the drive (that fades to matte in a couple of months - I asked and then I went by my neighbours who used the same company some months back to verify) and lack of a booking schedule. They have to come based on weather/precipitation, so there are no set appointments and that's a little hard to plan with. The temps should be over 8C to do this so don't wait too long into the fall to get it done like I did last year.