I don't really trust any of the marketing (including videos) or friendly articles about how far along companies are. The best way to judge I've seen is by the mandatory reports companies testing in California must supply. By those, Waymo is far, far ahead as of 2016. They've driven 635,868 miles (two orders of magnitude more miles than their next closest competitor) and their miles driven per disengagement was 5,128 (an order of magnitude higher than the next closest, with many still in single digit miles per disengagement). I'm eager to see 2017 numbers. Perhaps one of the other major companies has caught up but I'm doubtful. That's a wide gap to close in a year.
Sure, the numbers could be gamed a little (just drive on the same road you can do perfectly every time every day all year) but doing that will never let you improve your real world performance (important for the big companies heavily invested in this, not so much for the smaller companies looking to get acquired).
I think it's reasonable to just ignore all the small companies working on this in stealth. It's all about testing for self driving cars. They can't perfect it just sitting in a garage and thinking really hard about what problems they may encounter and maybe a few prototype vehicles. They need as many cars as they can on the road driving and collecting data on real world situations.