Sclerotherapy has been the most effective cosmetic treatment I have undergone. For the cost, it yields great results and they are lasting...over three years passed before I needed a touch up. If you have spider veins, you will be very pleased with this procedure.
Downtime is minimal. The most annoying part is wearing support hose and not being able to take a shower for 48 hrs. Do it on a Friday and winter is the best time because of the hose you must wear for 48 hrs :)