You guys said feedback is important so here's my two cents.

You can't make people use downvotes as much as upvotes no matter what, imo. More downvotes maybe, but still only a fraction of the upvotes. That's why everyone will keep going up, quite rapidly, as the system is now.

I was surprised about how easily it was to rank up. It shouldn't be like that, and I don't believe downvotes will fix the general trend, it will only maybe slow it down a bit.

Maybe it would have been better to make it harder (multiplied by 2 or 1.3, or whatever, you decide is the right number) to reach the next level than the one you're at. Like Hive rep system works (sort of), or Rising Star. Easy to rank up the very first few levels. Much harder at higher levels. That of course can still be changed, even now after being used for some time.

Something additionally, which may or may not be a good idea (I know it was discussed in the S. days, but I don't remember why it wasn't implemented), is to slowly but continuously drop in reputation (every day or every week). That's an incentive to stay active to keep your reputation and long inactive people will drop in reputation and will need to start over when they come back. This is for @blainjones too.