I buy & try A LOT, mostly Nordstrom online. This is because returns to the store are super convenient for me, there's no deadline for returns, and it is only a matter of a phone call to get an adjustment on my purchase if the price goes down. I think I am also pretty good about returning stuff that isn't quite right, and on a few things I've agonized for months.
I almost never buy anything where I will have to pay for shipping unless I am 100% certain it will fit. I took a huge leap of faith last week (by paying shipping) when I ordered a bra using a recommendation on bratabase.com. I also ordered very cute, very marked down socks with it to give as gifts, so all won't be lost if that bra has to be returned.
Also, when I finally buy something that has been on my list for a long time (chambray shirt, I'm looking at you!), I often find I wear it less than I originally envisioned. By the same token, the serendipitous purchase gets worn to death. Go figure. [And does that mean I should buy the Leith pleather midi-skirt that Angie featured a few months back since it just went 50% off which means the price is reasonable for a slightly ridiculous purchase?] Oh, and I think the chambray shirt would *go* with it okay.