The only time I really shop online is when I cannot find it local. I'm a big fan of buying things local to support local business, retail stores and employees at them.
Sometimes I find the prices on
Amazon to be a little cheaper, but not enough to warrant me to use them on a regular basis. I also do not like Amazon's stance on taxation and failing to collect most locale taxes on purchases.
All that said, I did buy a new HTPC case for our home theatre for about $180, but again, it was mostly because there was no place to buy it local. I do use online reviews a lot, especially on my phone where I can scan the barcode of something and see the reviews instantly.