I have used livehelp and phplive both work fine but livehelp offers a windows application to manage chat sessions not sure if phplive does yet... not checked in a while.

My vote also goes to Kayako's SupportSuite Software. It's pretty, reliable, and works amazingly for both the customer, and the webhost. It's been my favorite over StarDevelop, and phpchat and stuff like that. You get what you pay for, and in the hosting business there are thousands of other companies, so great first impressions are a must. Goodluck.

Regards, Anthony Bush.