I've used Antec cases and power supplies since I started assembling computers. Their reliability and competitiveness still keeps them on my short list when shopping for new parts. Each one of the 7 computers in my home are powered by Antec.
As for why I like Antec's products, I have two reasons.
1. They make good stuff. I don't think I've ever had an Antec product I was unhappy with.
2. For my 18th birthday, my mother bought me the case I'd been wanting for a year - an Antec SX1030. It was expesnive then - about $150, as I recall, and she was being treated for cancer, so it wasn't like we were swimming in money, but I think she knew it would make me happy. This was the last gift she ever bought me, as she passed away about a week before my 19th birthday. To this day, 11 years later, my primary computer is still housed in that same case. I'm quite fond of it, as it's served me well for those 11 years, but try as I might, I can't come up with a reason to replace it because... well... it still works.
Two words come to mind whenever I hear Antec- practicability and reliability. The tough decision has always been which model to buy for your needs, rather than worrying how the product will last or how it will perform.
I love antec cases and power supplies as they always provide a great products with a great price for what you get. When buying an antec unit, you can be sure that you are actually getting something worth what you paid.
Been using Antec products since I started building my own PCs 12 years ago. Currently using the following Antec products in a few of the computers laying around: 2*P280s, 1*P182, 1*NSK2400, 3*620 watt NeoEcos, 2*520 watt NeoEcos, and a 650 watt EarthWatts. Solid stuff.
I haven't tried an antec case yet but would love do a new build in one of their cases to see how they compare. As for their PSU's, I've owned a couple of the earthwatts units and generally found them to be a decent value and reliable.