Gmail offers easy and simple email usage. The account is user-friendly, settings options are easy to understand and edit, themes and experimental additions allow the user to personalize the account, and Gmail's Buzz feature is a Facebook-like addon. Very good site!
Very flexible function, great "priority mail" filter, great anti-spam filter, just all around excellent. The only down side is no built-in way to download you email history. Use Thunderbird of some sort of old-fashioned off-line email software in conjunction with Gmail to work around this.
Keep in mind that nothing is sacred in this free email service from Google. Personally, I love the massive inbox, and the spam/junk mail filter has admittedly improved significantly from Gmail Beta.
However, read the Terms of Service closely, as Google retains the right to read your emails for the purpose of building a personal profile on your web usage data, interests, communications with friends/family, peers, etc... and feeding all this data to their AdSense advertising system, which displays Advertisements across the top, down the right hand-side and potentially elsewhere on the pages in your Gmail inbox.
There is no simple way to turn off this automatic tracking and advertising, nor does there seem to be a simple way to opt-out. The ads are eerily on-context to the email you are reading, but often so much so that they become too creepy to be worth clicking. IMHO this does not enhance the experience as some claim, but many (myself included) find themselves stuck with Gmail for lack of a better alternative with as much free inbox space and high maximum Email Attachment file sizes.
If Google gave finer-grained, more transparent, simpler controls for limiting what types of emails the Ad server can read, and where ads can be displayed, I would change this critical review quite a bit, because that aside, it is quite a good product.
free? sure, "free". Only give up your privacy and get email less awesome than fastmail.fm. google is PRIMARILY an ad serving entity. chew on that you sheeple! gmail filtering features continue to suck. why?