I was looking to get an idea of past experiences with different helpdesk software.

Anyone have an opinion?

The Search feature should help you a lot in reading past experiences with different helpdesk softwares !

I currently use WHMCS which is a billing center and helpdesk all in one. It is quite useful. Another one that I have used is Kayako.

I would do a search for helpdesk in WHT I have seen alot of threads like this. But, we use perldesk.