Hi, David!
Be Our Guest Restaurant is the newest, hottest dining location in Walt Disney World, but you don't need to make a reservation to dine there during lunch hours. At that time, BOG is a Quick Service location, with an entirely different menu than what's offered during dinner.
That being said, I would take a look at both the lunch and dinner menus to see what you'd like to try most and take it from there. Keep in mind, I'm the crazy lady who took 400+ high school seniors to WDW in April and ate at BOG for an early lunch at 11, then went back for my 4:00 chaperone dinner reservation. Hey, I wanted to sample them both! ;-)
IF you have your heart set on dining there for dinner, then I would be sure to obtain Advanced Dining Reservations. Even during the off-peak seasons, this will still remain a popular dining destination for so many folks who simply haven't gotten to try it yet, both locals and repeat vacationers who are visiting for the first time since BOG's December opening. Snag an ADR if you can, David; then you won't be disappointed once you are there on your trip.
To be honest, I thoroughly enjoyed both experiences that day, as each was quite different from the other. Both, however, were delicious and memorable due to the incredible amount of details in the space, the changing use of the space, based on time of day, and, of course, the fare offered. Try them both, if you can!
Send more questions as you think of them, David; we love to help!