It's all up to you dude. To be honest, I don't have a Tumblr myself, so it makes no difference to me. However, I do watch a few of them closely, so if you ever did make one I'd probably follow you. Still, it's more of a matter of "do you think you want that kind of responsibility". Either that or it's a "do I want to update something else as well" kind of thing. Still the choice is yours and yours alone to make. ^_^
If anything, it's just a quick and easy way to connect with your fans. Yes, there are more unsavory parts of tumblr (as is deviantart and youtube and facebook and twitter and...) but it isn't hard to avoid them.
You should. It an amazing way to promote your art work. I know a few artists on DA using Tumblr to promote their work, and even just to display it. On Tumblr, people don't expect you upload stuff, so you don't have to worry if you don't. You can do whatever you like, and even reblog other things And it's not like Facebook, or DeviantART. People like "Like" and "Reblog" your art, but they can't spam with you comments If they reblog it, it'll say "source: (username)", so people will know where it came from It's quite easy to work your way around And you can "Follow" people, much like you "watch" then on DA
I'm probably really bad at convincing people, but yeah Even if you just give it a shot. Couldn't hurt
My experience on Tumblr could definitely be classified as interesting. Good interesting, to be clear. Sure, I may have stumbled into some dicey territory, but I think that could apply to any social networking site in general. And yes, it does have the potential to make time speed up. In the end, if you feel compelled to join, by all means go for it. I've been on Tumblr for almost a year and have had no regrets about it.