Im not sure how helpful this will be or if this has been covered by others, but after spending way too much time trying to get a brand new (as of 4 Jan 15) MBP 13 Retina to connect to our home wifi, I want to share in as many places as possible what worked for me.
Our home network is a Verizon FiOS setup, with the MI424WR router in its stock configuration. This means WEP security (why is that the default?). I kept meaning to change it, but the trouble was just a bit too much to deal with until this came along.
Quick note: I checked the MBP wifi connectivity on my work network and it was perfect. Immediate connection, no drops. We use an AirPort Extreme with WPA2 security there
My fix was simply to access the router and update to WPA security. Connected immediately and its been rock-solid and stable. Bonus for us is our older iMac (7,1 running 10.9.5) was having intermittent wifi issues, but is now also much more stable.
Hope this helps someone else!