I've been using it just about from the start, and I'm very pleased with it--I have multiple accounts, even. The search-don't-sort gimmick hardly takes any time to get used to, and I find it very useful. The labels feature gives you the same basic convenience of traditional folders. I really like the archive feature; it's nice to tuck things out of the way forever (unless I want to see them, in which case I can search/view All Mail/view by Label). My old Hotmail was all but abandoned.
I have one account just for business/e-transactions, one for personal mail, one for stuff neither business nor personal (such as forum registrations), and one as a "file locker" that I share with friends when I want to transfer files (kind of like Yahoo briefcase in principle) I know Hotmail and Yahoo, etc, have similarly large account limits now, but the 2.8GB (10MB attachments per mail) really comes in handy.
The spam filter has been very effective. I have never seen a single spam in my inbox OR spambox for the business, file locker, and personal accounts. I'm careful with where I submit my personal address to, but I'm very impressed with how spam-free my business account is, considering how many different vendors I've purchased from over the years.
The personalized ads that appear to the right of messages are non-intrusive, I almost never notice them. They're just text, no flashing gifs. This is a non issue if you're using a client; it works great with Mozilla Thunderbird, and presumably similar clients such as Outlook Express.
Go for Gmail, it's well worth it.
(No, I do not work for Google. )