For a lot of my genealogy research I use the National Archives in Washington DC, most frequently since I live only 30 minutes away from Washington. Also I need to use a facility such as the Archives because I research multiple states. I envy those (sometimes) who live in the same state that they research. Fortunately because I also research Civil War soldiers, I have easy access to those wonderful pension files. BUT---when I travel I always use the State archives when I can.
Not being close to the counties that I research, courthouses are less frequently used, except on those special research trips.
I am curious though, do many of you use courthouses more frequently, or Family History Centers?
For African American antebellum research courthouses are a must, to have access to wills and early deeds, manusmission.