I'm a huge fan of Joe's BBQ, and Joe's Farm Grill is okay, but not the best.
First, the physical facility, while quaint and has some nice history behind it, is just uncomfortable and very oddly organized (drink stations outside, other things inside). The trash cans suck royally. While I can appreciate the effort to drive recycling, having a trash can that has shapes for everything is just dumb. It results in piles of trash near the entry of them and not good for when you take a tray full of garbage to the can only to have to find a place to set it down to sort.
Food -- good. I think the burger and the pizza are probably my favorite here. Oddly you'd expecte more carryover from Joe's BBQ as far as BBQ options, but there isn't -- didn't bother me though. Sweet potatoe fries are great as is the dipping sauce that comes with it.
Shakes when in season with fresh berries are yum. Desserts sound better than they are, so I'd pass and head to Nielson's if you want a dessert instead.
As a place for larger groups it stinks -- tables are crowded and small. If you want to sit outside that may be fine, but the huge trees sometimes attract unwanted insects :-).
Overall okay if you are in the mood for something different.