Ten of millions of users worldwide cant be wrong, Gmail is a solid product.
Of course, it is free, and you get over 7GB of storage space.

But there is more to it than that. Gmail is all about having your information, your precious information, stored online rather than on your home pc where it is vulnerable to theft, breakage, power spikes etc. Yes, you can use Outlook or another form of email software but these do not protect you from the ravages of life as they generally reside on your pc. I think this one single point is invaluable. If you are serious about storing your emails safely, store them online.And who better to store them online with but one of the world's largest organisations - for free.