Since I threw together a list of the GOOD companies I figured I should probably put one together for the not so good ones. Luckily, the list is much shorter.
California Air Don't get me wrong, I think their compressors are incredibly quiet... when they work. The better half got me one for Christmas and it didn't work right from the begining. It won't restart all the time when the pressure goes down. I think I've narrowed it down to a heat issue but I'm not sure. It seems that if it runs to pump up the tank, you empty the tank as quickly as possible, it won't start back because it is too hot. Most of the time turning it off and back on will get it going but many times it has to sit for a while. Customer service is very slow to respond unless you call them and want me to ship it back under warranty which they will take care of IF they believe it is their problem and not something I did.
Oneida Air I'll start by saying my father has a big Gorrila and likes it. They did his DC design and for the most part it works. Myself, on the other hand, have had nothing but problems with their customer support ( Picking up a pattern here yet? ). I wanted to get a cyclone for a Grizzly 2HP DC so I found their Super Dust Deputy. Seemed like a great solution, but I needed to know the actual size of the inlets and outlets because everyone calls something 5" but no one is using a consistent measurement. I called, got a lady, she said she would check and email me. I got an email saying they didn't know the size other than 5". I replied nicely stating I know 5" but what EXACTLY is the measurement, 5.1", 4.9", whatever. No response so I called. The next person got irritated with me and said it is 5". Again, people, can you just measure one??? Nope...
Hopefully I won't have any more but you never know.
Things happen, I get that, stuff breaks, etc, but it is all in how you handle it. Handle it well and I'll be a long time customer, handle it poorly, and I won't deal with you again.