In my own experience the best CRM for Gmail contacts is Contactually, which has full Gmail integration. Most importantly, it generates leads and contacts from your Gmail contact list automatically and dynamically--meaning that the minute you contact someone or they contact you, they're captured in the CRM system and data is collected on them.
If you are on your way testing solutions for best performance, I would like to recommend you webCRMs free trial, because it fits your main listed requirement.
Bubba, a good example is BPMonline CRM with new engaging interface. As many other CRM applications it can handle Leads, Opportunities, Accounts and Contacts, Campaigns and Reporting and has out-of-the-box features for notes, reminders, call backs, as well as it is provided with all must-be-tools for full integration with Google Contacts.
Try it at www.bpmonline.us