MK actually has my FAVORITE CSs! Columbia Harbor House and Cosmic Ray's! They are both great IMO! As previously said, do try to sit upstairs and either look out over HM, or on the overlook between Fantasyland and Liberty Square. We ALWAYS make a point to eat here at least once during our trip (last time we did a couple of times). My sis and I sat up there during spring break this year and watched the line for HM get longer and longer. The CM kept pushing the "Line Starts Here" sign back (it was a VERY busy time of the year to go). It was so nice and quiet

, that was our "refuge" in the hustle and bustle of everything.
I also love Cosmic Ray's for dinner (usually a little bit later of a dinner). We like to sit in the dining room where Sonny Eclipse performs (cheesy but fun

). We've eaten at Pinocchio Village Haus once or twice in years past, and enjoyed getting a table at the window which overlooks IASW, but haven't been to it since they have a new menu (pizza now I think?). Also eaten at Pecos Bills, which was okay too. Both Pecos Bills and Cosmic Ray's have "fixins bars".
We have SOO many snacks that we like in MK too! Most FAV is Aloha Isle

, where you can get Pineapple Dole Whips

, followed closely by Sleepy Hollow and the wonderful ice cream cookie sandwiches!

DH and I also love to get cinnamon rolls at the Main Street Bakery, which are HUGE! Of course you can't miss the Churro Wagon in Frontierland

...I can go on, but you get the point. My sister and I actually did the QS dining plan over spring break and paid for two TS meals (one breakfast at Cape May and one lunch at Whispering Canyon which were both WONDERFUL!) and really liked it! We actually felt free to come and go as we pleased without worrying about what time our ADRs were. It's a nice alternative.