You're not the only guys trying out not particularly well established browser tech on your users. cloudsigma.com are also using websockets for their web based interface and it's buggy too.
I'm using modern browsers like Firefox and Chrome, to no avail.
Having to change strange options like network.websocket.allowInsecureFromHTTPS to true in Firefox's about:config indicates to me that you're mixing HTTPS and non-HTTPS requests, which most browsers take umbridge to, so I'm not surprised there are issues here.
My first login attempt doesn't echo my typing, and the second shows ^[ before each character. I'm still unable to login.
Reliable console access is paramount. Linode.com have both a working, reliable web based console as well as the ability to ssh into virtual machine's host.
As a potential new client, having the basics ironed out, before launch, is vital, in my opinion. It instils confidence, rather than doubt.