Undesirable is totally subjective. In general, people are referring to Midwest programs in small cities, with cold winters, few restaurants/bars, and little entertainment. Basically, anything that isn't a major city or on the coasts. But you might be from Nebraska and you like small cities and hate cities like Chicago, NYC, or San Diego.
Surgery is, in general, DO unfriendly and If you go to a DO school and want to do surgery, you'll likely match at an AOA program, most of which are located in Michigan and Ohio. You can search DO residencies here
http://opportunities.osteopathic.org/search/search.cfm
Acgme derm, rad-onc, orthopedics, urology, ENT and, maybe, opthmaology( some ACGME programs take DOs for opthmaology , like gesinger) are pretty much impossible as a DO.
There are AOA residencies for the specialities listed above, except rad-onc, but there are few spots offered each year. 93 ortho, 20 ENT, 20 urology, and 14 opthmaology spots were offered in the 2012 match.
http://www.natmatch.com/aoairp/stats/2012prgstats.html