I agree on a 3D helicopter or bigger aerobatic plane, sure big difference and worth the money.

On a trainer or 40 size, I think it would be a waste of money and battery drain. For those of you that don't know, digital servo's have a higher current draw, even at idle, than standard or even hi torque analogs.

I'm not saying they are bad. They surely have thier place. I also agree with the buy the best you can afford, it saves in the long run from buying twice. But I wouldn't worry about it for slow flyers, mild aerobatics etc.