My thoughts are that when a system comes out and there's a digital service, you know a sale is going to happen eventually. When the sale finally happens, usually something you remotely want is on sale, since it's a small library of stuff at first. So I feel like it's better to wait and save money when the small pool of games goes on sale at some point. (Even though it's a bit of a surprise there was no E3 sale)
In addition, it seems like majority of eShop content is about $5 or so overpriced.