Mrs. Steelhead:
First, I'll avoid answering your question by saying that the Freeman is 100% C&R on grayling.
But yes, I have had grayling back in the day. They were good eating, but definitely not my favorite. Brook trout from a creek can be very very good and are #1 with me. I tend to release my cutts and rainbows.
Grayling in general come from colder, clearer water (notwithstanding muskeg, tea stained boreal forest rivers that AB has a lot of), so they do taste pretty good. Any stream caught salmonidae usually does. Some guys think they have a bit of a nutty flavor to their flesh.
Cheers,
Smitty