I have used, Maximizer, SugarCRM, Vtiger, and Act. Act is the best except for 1 thing. E-mail options! The concept of the Outlook integration is great, but I find it breaks a lot and I'd just as soon use my gmail(google apps). It is astounding to me that there is no way to change the ports/use SSL, TLS etc. I'd love straight IMAP but I'd even settle for secure POP3!