>And then suddenly, you got a GB of storage. For free. No questions asked. And its UI was simple and easy-to-use. And you could search it.
Also don't forget that Gmail at the time had the most intelligent spam blocking algorithm compared to AOL/Yahoo/Hotmail/etc.
It was a big enough deal that some observers that switched to Gmail considered the email spam problem as "solved" because Gmail seemed so good at it. (On the other hand, many independent people trying to run their own SMTP servers think that Gmail is too aggressive with spam filtering because it also blocks many legitimate senders with low/unknown reputation.)