Yes, I've missed items before and been really, really bummed out about it. I usually do NOT buy items full price, but whether or not I splurge early depends more and more on where I'm buying it from and whether I think I'm likely to really regret an item that I missed because I was waiting for it to go on sale.
The bright ATL scarf that I fell in love with, as well as the pumpkin cardigan that I can't stop wearing, were both going out of stock FAST. Fortunately I had a gift card and discount coupons, so I didn't feel too guilty.
The Tarnish peacock scarf was one that I hoped would go on sale last year, but really regretted missing out on. At the Seattle YLF meetup, Angie mentioned that it would be quite unlikely to go on sale, so I decided to snap one up before they went out of stock.
For other items that are more widely available (such as Clarks shoes, which can be purchased from a variety of vendors, or staple items like Gap jeans) I'm willing to wait a while because I know that the price will come down eventually, and they are highly unlikely to sell out quickly.