Just got the Firefox 49 update (yay!)
But Netflix still wants to install Silverlight (boo!)
How can I watch Netflix in Firefox, as has been advertised?
As wisely mentioned in comments: if you have this problem, contact Netflix support about it. It's a problem to be fixed on their side, and the more complains they'd get, the faster it get fixed.
A solution by GizmoChicken:
Is anyone able to play Netflix? With the original user agent it requests to install silverlight With chrome user agent it plays, but with tearing and high cpu load.
Netflix plays for me on Firefox 49 when using the following User-Agent entry:
Linux / Chrome 53: Mozilla/5.0 (X11; Ubuntu; Linux x86_64) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/53.0.2785.34 Safari/537.36
Sometimes I have to hit "refresh" to start a video. I don't recall ever having to do that with Chrome. So it's still not perfect.
===================================== (edit by OP)
Before using the user agent string above (which worked) I had to do two other things.
Then just select the Linux / Chrome 53 user agent, go to Netflix.com, and Bob's yer uncle.
Edit 2: This also works on 32 bit Ubuntu! Woo hoo!
Edit 3: At least as of April 2017, 32 bit no longer works, but the user agent workaround is no longer required.
Edit 4: One of the many awesome enhancements in Firefox Quantum is that Netflix works again in 32 bit! (Dec 2017)