no, the last time i used it was on a nforce board in xp, teaming was supported and in theory boosted your network speed and ping times, i know with intel nics you can combine them but not it really sure how much it would help unless your building a server. most of the evga boards use a intel and a killer nic, the killer is supposed to help with gaming traffic for online play but the reviews have been mixed if it really does.

i run two on my server, free BSD based, and my throughput increased by 60%, basically my server shares will run about as fast as sata 1 speed for transfer rates. i looking at some 10Gb stuff now, nic cards and switch, on the secondary market, the prices are still pretty high but the network speed is crazy fast.

The KillerPro network cards worked really well at unloading traffic from the CPU. Then Qualcomm bought the company and everything went south after that.

I have never used dual NIC or ever needed a backup one. I would take more USB 3.0 slots over extra NIC.

I don't game much, but never have used it on any of my boards.

Ran one as a DHPC server and router so I could do internet passthrough @ LAN, running my laptop from my desktop when ports on the switch were at a premium. Although, in complete disclosure mode, this was back in the XP era.
I don't think I've used dual NICs on a mobo for a decade. 

Another possibility I thought of is the following:
 
Gigabit internet services (Google Fiber, AT&T Gigapower, etc.) are available in some areas.  The ethernet interface seems to have some amount of overhead.  Therefore if you had a 1 Gbit internet connection to a 1 Gbit ethernet port, I'm guessing your max speed would be limited to 9XX MBit due to overhead.  Maybe there would be a way to use dual NICs to realize the full 1 Gbit?
 
Then again, at that point it would probably be easier to include a 10Gbit ethernet interface on the motherboard.

Special K
Gigabit internet services (Google Fiber, AT&T Gigapower, etc.) are available in some areas.  The ethernet interface seems to have some amount of overhead.  Therefore if you had a 1 Gbit internet connection to a 1 Gbit ethernet port, I'm guessing your max speed would be limited to 9XX MBit due to overhead.  

Most speed tests don't include the overhead of every packet, only the payload. You may well be saturating your 1gbps link but measuring 0.99gbps of throughput. Your ISP's service is a function of the whole packet, not just the bit your speed test is interested in. In the case of "gigabit", assuming it's "gigabit ethernet" all the way, this isn't some arbitrary limitation, it's just how it works. 

Trying to load-share across two NICs, depending on how it's done, could make things worse. For example, if it exacerbates packets arriving out of order it necessitates re-ordering at the other end of a flow which causes delays (while it waits for missing packets to arrive) and much memory copying to hold on to the early packets (which is slow). When bigger networks have multiple links in a span they try hard to keep all the packets of an individual "flow" on a single logical link at every stage in the network precisely to avoid this sort of issue in end-user systems.