Sticking with the original 3 companies, Spyderco, Kershaw, and SOG, I'll give a few opinions from both using the knives and the customer service.
Out of the three, I'd say they all specialize in different categories.
Spyderco is what you go to when you want a high quality production knife that typically runs around $100-200 depending on how much of a spyderholic you are (myself included

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-Excellent customer service, you can speak directly with the owner and his staff here in the spyderco forum (one of my favorite companies :thumbup

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Kershaw has a TON of knives well under the $100 mark that are all great to have and use. I still think the new G-10 tyrades could have easily been as much as the ZT 0200's and most sell for 2/3 of the 0200 price.
-Excellent customer service, you used to be able to speak directly with the staff here but can still discuss at the kershaw social group.
SOG has it's fixed blades. Their assisted openers could use some adjustments, but the arc-locked knives are very nice IMO. The Vulcan is a very good deal if you ask me. The only problem I see with SOG is that it seems that the folders get the back burner.
-OK customer service, depends who you speak with, Chris here is a great guy, but there's horror stories of a lady who answers the phone at SOG :foot: