There have been a number of articles published concerning problems with the Surface Pro 3 and Wi-Fi connectivity.
I purchased my Surface Pro 3 at the Microsoft Store in Atlanta the day they were introduced on June 20th. At home I have a NetGear Nighthawk R7000 AC 1900 router on a Comcast cable modem. I’ve never seen any WiFi problems whatsoever. Testing on my home setup with an AC connection, my ping averages 10 sec, my download speed averages 30 Mbps and my upload speed averages 6 Mbps. Those results are very consistent. I connect with no problems to WiFi wherever I go throughout the Atlanta area. Speeds vary of course, but connections have been reliable. I’ve connected without problems to WiFi at the public library, the bookstore, several restaurants, the doctor’s office, the dentist’s office and several shopping malls.
Edit: After reading the above I need to add the caveat that since I’ve been running the Windows 10 preview that I’m running a different version of the operating system.