They also don't celebrate birthdays, don't get tattoos or piercings, don't donate to any charities, participate in halloween (I guess in reference to the witches/magic/demons aspect)...

'heretical' is up for constant interpretation. Magic is just sufficiently advanced technology.

My experience w/ JWs is relatively light, I went to school with a few and they were decent people but we were perplexed at certain things (like not knowing their exact birthdate).. I ran into one a few years later who had left the religion and was full of piercings and tattoos working at a skate shop. Talk about rebelling against parents eh?

One of my friends got married to a JW girl and pretty much dropped off the face of the planet working for an IT company a few hundred miles away... (so yes, not totally against technology, you're right)..

It's really just a doomsday cult that encourages self-isolation and group-support mechanism. They've moved far away from the Watchtower days of trying to spread the message. Wouldn't be surprised if they've gone full Utah and started cataloging DNA and building a multi-trillion dollar ARK.