Free gigabyte, for real!
Numerous reports, along with the Google's publishing of an easy to spot April's fools announcement, seem to indicate that GMail is real. And they even have a sign in box now!
Matthew, who was also wondering, I'm glad ;-) reports on a screenshot (which itself might be an April's fool, isnt'it?) showing...nothing special.
What would make the difference for many people is having their whole email history at their fingertips: until everyone's computer is fully indexed (and I'm wondering why it's not yet the case), being able to quickly search all your messages will make all the difference.
Google seems to really be listening to what people want, as opposed to forcing stuff down people's throats. This should make them more and more popular, so let's hope they continue to not be evil in order not to become the next unfriendly giant.