The only problem is the user interface -- it has a goofy unintuitive UI that makes it pretty cumbersome setting up complex profiles. I'd pay another $6 for a decent editor on my actual computer. (It's tempting to write one, as tasker saves and loads its profile scripts as xml).
That all being said, here's the things that I currently use it for:
- When headphones (without a microphone) are inserted, and there's no media already playing, immediately launch my last music player and resume the last song.
- Mute the phone on sunday during church time, and restore the volume afterwards.
- Mute the phone if it's being charged after 10pm. (I always charge it while sleeping, so I figure if I'm up after 10, I want it to ring until I put it on the charger. And if I'm charging during the day, I want to hear it).
- It checks my work calendar, and automatically mutes if it's during the time that I have a meeting scheduled (and restores the volume afterward)
- If Sara's calling, it vibrates with a crazy different pattern, to make it more obvious that it's her.
- If I get a call that's a non-217 area code, and not in my contact list, it's a different ringtone (I've gotten a lot of phone spam recently, so this makes it obvious it might be spam)
- If I get a call from a number I've previously marked as spam, it doesn't even ring.
- If I text a secret code to my phone (or Sara's), it turns to full volume, and rings like crazy (to help find the phone if we've misplaced it, or if I know Sara muted her phone and I need to get her attention)
- If I receive a text message, and I'm in the car (based on being connected to the bluetooth device in my car), it reads the text aloud over the audio.
- If I get a text message, and I'm not at my desk at work, it forwards the text on to my pebble watch. (If I'm at my desk, I get the text notification on my computer, so I don't want it to bother with my watch). To check whether I'm at my desk, it does a web query to a URL I set up on my work machine that simply reports the time since the last input. If that number is bigger than a few minutes, it assumes I'm not at my desk.
- I haven't finished setting this up, but I want to do the same thing with gmail -- if I'm not at my desk, forward the message summary (First few lines) on to my pebble watch.
That's just a tiny sample of what this thing can do. There's a thread here on Reddit with people listing cool things they've made it do, and some other interesting samples on Tasker's site. Like I said, if you have an Android phone and you enjoy futzing around to automate your life, Tasker is absolutely worth it.