I have. Started with CRKT when I was young and it was all I could afford. Bought Benchmades because Grandpa always said they were the best, did some research here and realized how awesome Spyderco's were. Spent many many years carrying only Spyderco. Tried out Blade Tech, Benchmade, Strider, and some others for a short while. Enjoyed some of them, hated some others.
I've always owned Spyderco, but have come back again to carrying nothing but Spyderco. No other company has the materials, workmanship, and ethics than Sal and crew, and I will support them with a round hole clipped to my pocket from here on out. My current flavor is a Paramilitary that I am really liking, but as another poster said, it is really hard to beat a Delica for a solid, easily carried EDC knife.
I have also furnished family and friends with multiple Byrd's over the years, they are a fantastic value for the quality they provide.