Rickbull, I just upgraded my Early 2011 MacBook Pro to 16Gb of (Crucial) RAM without any problem at all. It's purring like a kitten.
I've been itching to upgrade it for a while now, and decided to take the plunge last week upon seeing how far RAM prices have dropped. Hard to believe that I'm entering into my 5th year with the MBPro, but it's still taking care of the business that I need.
I can't say that it's made a huge night/day difference in the operation of my MBPro, but it's nice to be able to devote more RAM to my Windows 10 VM while keeping a full slate of OS X apps open alongside it. Heck, I may even just be able to create a little 3 or 4 node network (VMs) to play around with, all being based out of my MBPro!
And FYI: my previous 8Gb RAM was fully being utilized by OS X with Photoshop/Word/iTunes/Photos open. Now with 16Gb RAM I find that I have about 5Gb free with those programs open. I know part of the deal with a *nix OS is caching and stuff for speedier operations, but stick this info-bit in the 'good to know' pocket. Hahaa.