http://www.womenrussia.com/fiancee_visas.htm
The above site seems to have good information on K1 type visas.
Details like a 3 to 4 month processing time, if you need a lawyer then use only a lawyer based in the US, 60% of such visas are approved, etc.. No idea where they got their information, but it may be of some use.
A related question: Anyone have any idea about the situation where once you are on the list for processing of a visa from the DR, how many people do they process on average per month? We are about 2,500 on a list of 16,000 waiting for an appointment date this month. This is after already waiting for 10 months.