Pros
I've only been working at IXL for a few weeks now, but so far I feel incredibly lucky to have found this job. The work I'm doing is challenging, interesting, and rewarding, the hours are flexible, and everyone at the office is very smart and friendly (when I find myself in the elevator with someone I've never met before, they almost invariably introduce themselves to me). The office itself is beautiful and inviting (without resembling a college dorm, as some other tech companies do), and the company offers some nice perks (yoga, massage, team sports, happy hours, etc.) yet doesn't seem to expect its employees to live at work in exchange. I also love that IXL is very committed to providing high-quality educational content - not just fun, flashy games, etc.
Cons
None yet, though I expect it's inevitable that some cons will emerge with time.