Squirrel Mail looks nice, but are you sure it's Ajax, i thought it was PHP based :/

You are right. Squirrel Mail is PHP based; (description in list clearly mentioned it ) …

I usually forward my emails to a Gmail account but as I have cPanel, I think Squirrel Mail is the best one to use. I've had no problems with it when I have used it and it does the job.

I never used webmail. I used to forward all my email to gmail/live

well, I've used Squirrel some time ago but now I don't use webmail, rare, really rare

I honestly love using cPanel even If I am only offering Email Hosting. Since it includes 3 webmail things.

That is webmail.

I like Roundcube purely because it has a more modern interface.

SquirrelMail is quick an easy and just gets the job done.

Squirrelmail wins over Roundcube in all aspects except the interface.

Squirrelmail is speedy, doesnt eat much of the resource compared to roundcube and horde which is why its the most widely used.

another one that cpanel offer now is ATmail, which i like and have had positive feedback from my clients on this. i now just provide my clients with ATmail and Squirrelmai as webmail options

Smartermail is great client. Easy to use and maintain clients, accounts, and domain. It also allows for GreyListing on individual accounts as well as across the domain.