It looks like it has all the basic photo editing features in addition to the gimmicky features like stickers. It seems useful to me if you don't have Photoshop (and you are using Picasaweb).
But what if the semantics change and it's called "Subscribing"? Does that affect your assessment? I think a lot of folks are treating this as a donation (which is a side-effect of them using PayPal for this) and that's tainting their perception of what this is all about.
Conde Naste is a huge corporation, and if they want to let their purchase go down the toilet... well, I'm sorry, but I won't be picking up their slack.
I wouldn't donate either for those reasons, but one thing to keep in mind is that the codebase running reddit is open source: http://github.com/reddit/reddit
They pushed to the public Git in a month, but the donations users are making will go towards improving that codebase. It can be used to deploy your own (and hopefully more scalable) version of reddit.
That's only for people who visit your site, though, people from places like /r/programming. Let me tell you, there are divides between those who are savvy enough to understand places like /r/programming and those who aren't. I'd estimate reddit's overall adblock usage at being just the same as the rest of the news aggregation sites.
You need to first be blessed by the Holy Spirit, aka Paul Graham. Otherwise, you might even see the buttons, but your votes have no effect because you're an Outcast.
This probably isn't the full picture, but you can't vote down comments left directly in response to your own comments (for obvious reasons), nor can you vote down comments over a certain age or that are already of a very low score.