I don't download full 3DS games from the E-Shop because even if I did have a stable enough internet connection to finish the damn things in less than a month, they cost a fortune. I generally pick up my games pre-owned, since the only difference is that I have one tiny additional setup step of purging all previous save data. I don't mind the extra few seconds that takes when it saves me half the cost of the game.
I've downloaded a few of the smaller items from the E-Shop, including the Ambassador titles and a few things like Pullblox, Colours 3D, Zen Pinball, etc. I've downloaded my fair share, but only when the price is reasonable (not very often on the E-Shop, place is a damn rip off) and it's worth spending an age finding a net connection for. But as for full titles that are available in physical form, I'll always find them at a bargain price so there's really no reason to even look at them on the E-Shop. If it was mega-rare and only realistically available on the E-Shop (like back when Tales Of The Abyss was a nightmare to get hold of, even though it's been reprinted and it's pretty common now) then I might consider it.