Gmail, or Gmail?
That is, "gmail the email service" or "gmail the ad-slinging, perpetually obstructive web interface"?
Got my gmail.com email address back when it was "invite only", just to bring a little stability to an email life that was plagued by ISP buyouts and mass email changes. Contrary to opinions expressed above, I understood exactly what they were doing to "target" the ads, and the "labels" concepts was really helpful.
I want to make clear, that gmail has never been my only email. Just my only "casual" email, with other far less public accounts on servers I control for "serious" email.
Anyway, I found the ads frequently humorous, even charming. Who wouldn't get a chuckle about seeing ads for kilt rental and bagpipe lessons displayed next to a thread on functional programming?
As the IMAP interface approached useful, and the web interface started to feel more like being a tester for Aperture Science ( https://www.youtube.com/watch?v=DBfIyeb8kc4 ), the writing was on the wall. I only go to the web interface when I need to do a search that the IMAP interface can't handle, and I log out as soon as possible, as being logged into any google property wakes up the unblinking eye. Maybe enough users are like me that the ad-decorated web service just doesn't get enough use to justify the bad karma.
As for "$5/month for an email address" (claimed above), would that be in Zimbabwe? An $8/month shared host at a number of places (even GoDaddy, for masochists) comes with some number (>10) email accounts, and has for years. OK, maybe $10/month to cover the amortized domain registration so I cannot be forcefully denied an unchanging email address for infrequent correspondents, but divided among all the family and friends also using that email server.
Worry more about the search engines you use (my primary is DuckDuckGo, but I miss Blekko and hope they are being fed well in IBM's dungeons), and the "Like" trackers on darn near every site.