I tested darksend today!
I must say, I like it that you can premix your coins and then use that "dark balance" for sending anonymous transactions

Pretty impressed by the GUI as well.
My only remark (also related to the thing below) is that it took nearly 3 hours to mix 2 DASH... That seems a bit slow, but hopefully if we get more masternodes online, that won't be an issue anymore. But I'm willing to wait a bit. Privacy has a price, in this case it's waiting time.
If you're not running a version 0.12.0.55 Masternode, you're putting the breaks on when people are trying to mix. We still have about 18% on a different version which is messing up the mixing performance. Like hitting a brick wall.
So please update ASAP, thanks

Another thing I want to mention: when testing a transaction, it costed me 0.1 DASH as a fee. I know that with transactions, fees are involved, but 0.1 DASH (around 0.001 BTC or 0.25 USD) is pretty hefty. Will fees be lowered someday?