We just did MLK weekend.
We were in the parks Thursday through Wednesday, with the exception of Sunday which we took as our down day.
Thursday and Friday were awesome. Most things were walk on or short wait. We had lots of FPs we didn't use because we didn't need them. It did get more crowded Friday night, as weekend travelers came in, but it wasn't bad.
Saturday and Monday were crowded, but not horrible. FP rides had good waits, but with the use of FPs it wasn't a problem. Rides like Pirates and HM had short waits and were good options. We used a lot of these days to see shows and such too.
Tuesday and Wednesday were back to uncrowded, with a lot of the FP machines closed and most rides walk on or under 10 minute wait. I think the exceptions were Autopia and Indy.
The weather was beautiful for us, 70-80 and sunny. No rain. But it is January, and not every year is the same.