I just finished reading A Cappella Arranging and made that same cringe when I came to a chapter on writing medleys. Then the authors said exactly what I was thinking - that many people hate medleys, and that they can be cheesy and exhausting (for both performers and the audience). But they pointed out that medleys, when done well, can be fun and rewarding.
They also said that mashups, which I love, are a subtype of medleys. Personally I find them to be different enough that they should be separate styles, though they can obviously be combined. I'm currently working on a four-song mashup.
But their chapter made me realize that I don't really hate medleys, I just hate some of the crappy medleys people create. So I've decided, as a challenge, after I finish my mashup, to write a medley. I have a few fun ideas. I'm actually looking forward to it!
Deke Sharon and Dylan Bell should be commended for making me realize I don't hate medleys.