I had wifi problems after the update, also, although the symptoms were different from yours. I could get stable wifi connections with certain networks, but not others. For example, my work router puts out a network for employees and a separate one for guests. I could not connect to the former for more than brief intervals, and usually failed to connect at all. The later mostly gave no problems.
On the same router! The problem could be fixed temporarily by rebooting the router, but this was not a desirable solution.
I had experienced wifi connection problems on my SP3 for a long time previously, with both Win8.1 and the initial installation of Win10. The solution had been to roll the Marvell AVASTAR network driver back to version 15.68.3073.151 (12/22/2014). Unfortunately, this version was deleted by the November Win10 upgrade., and it is not longer on the Microsoft site. However, with a lot of googling, I was able to locate a copy and install it.
Presto! Wireless is working flawlessly with all networks tried, even though this driver predates Win10 by many months. More recent driver versions
15.68.9030.41 and 15.68.9032.47 failed.
I had described this fix on this forum back in June in another thread. Others have mentioned that the '151 driver works for many users (see, for example, Barb Bowman's blog:
Windows 10 WiFi Issues with Surface Pro 3 and Surface 3 | Barbs Connected World).
