Level 4.

I've given it a chance three times. Sometimes I manage to tag along on a NM, die a lot and get very little reward due to level difference. I'm sure if I tried enough times I'd finally get a lower group and scrape my way to levels where exp difference isn't an issue and I could start to enjoy it, but that just wouldn't be fun and I can't motivate myself to do it.

Rather interesting to see on the thread that most people are either level 1-6 and stuck, or 17-20 and swimming in lockboxes and crystals. No middle ground.