I turned down a job with them (mostly as I want to move back east and the job was only in sunnyvale, good location, just not for me at the moment). But the work they do is interesting, the compensation was competitive, and if you have a family some of their fringe benefits can be very valuable (employee discount at walmart, grocery delivery to the office could save lots of time...)
[1]https://www.walmartlabs.com/