DH and I are going for our anniversary trip and I agree that the prices at the sit-down restaurants are a little too expensive. You can get the same food off-site for half as much (then again, that's the way just about everything at Disney is!)
On my last trip, we only at at counter service places and i felt it was worth it. The portions are large, the food is good and the price is not too bad. DH and I plan to do just about all our meals CS and then have two special meals at a sit-down: 'Ohana and Whispering Canyon Cafe. We are using those meals as an opportunity to visit our favorite resorts that we can't quite afford to stay at.
My favorite counter service was Cosmic Rays at the MK. The food was good and there was a lot! I had a chicken caesar salad that never seemed to end! It was definitely the size and quality of a dinner salad at a sit-down restaurant for about $6.00 (at that time)
Here is a counter service tip: Try to find one that is nicely themed (though I think they all have some type of theme) so that you are still enjoying a fun dining experience. Also, by eating counter service, your meals won't take as long and you can head back to the parks!