Ever since Google launched the ability to disable Conversation Mode, I have been considering a move over to GMail. I had previously tried GMail for nearly a month but still couldn't live with the way emails were grouped together.
All my email accounts are domain based and previously I used FuseMail as my email provider and downloaded mail via POP to Thunderbird. The problems I was facing doing this were :-
1. Reliability with FuseMail was becoming an issue which isn't what you want when paying for an email service.
2. I tend to keep all emails sent to me, even after deleting them from my inbox, for future reference. With emails dating back to 2004, Thunderbird was beginning to lag even switching between emails, never mind searching.
3. I had to use Remote Desktop Connection in order to view my emails away from the office. As I am now out of the office a lot more, this was becoming a problem.