I got my Gmail account by an invite, but now invites are so commonly available it isn't really an "invite-only" thing anymore.
Gmail trumps Hotmail on many counts:
1) It memorises your e-mailed contacts automatically and auto-completes them for you so it's really convenient if you forgot an email. Hotmail on the other hand requires you to fill in the contact's details and what not, plus there's no auto-complete.
2) Gmail is fast, efficient and easy to use. Can't say the same for Live Hotmail... it feels cluttered and stiff by comparison.
3) Gmail auto saves drafts and saves your saved messages by default. Live Hotmail learnt this a while ago but Gmail had the idea first.
Plus many more... I love Gmail.
