I have a symmetric gigabit connection now, and I can barely max it out. My main machines are wired internally with gigabit, and my wifi supports 1.3Gbps across the backhaul.
The only time I've ever maxed it out is with five torrents running at once, and that only lasts a second or two, because then they're done. And we're not a light usage household. It's pretty common for us to have three or four streams all running at 1080 at the same time, plus other big downloads and videoconferencing. One main limiting factor is that I've never seen single service provider get close to gigabit speed (like updates from Apple or Sony for example). It has to be a swarm to get even close.
I'm not sure what I'd do with 2Gbps. The rest of the internet just isn't there to support fully utilizing that connection.
I also have 1Gbps and I'm able to max it, so long as the other end supports it (which is quite often). I regularly do it for downloads and for backups.
But generally, at 1Gbps, the speed bottleneck starts to move away from the connection between you and your ISP and towards your ISP's connection to the rest of the internet. At this point, most of the residential ISPs start to fall apart.
What providers have you seen full gigabit downloads from? In my two years with gigabit, I have never once seen a full gigabit download from any service provider not using swarm technology (like Steam does).
Google, Hetzner, OVH, Online.net, Feralhosting, linux package mirrors. Those are just the things I specifically remember.
I don't want to be misleading though, claiming "full gigabit" might be a bit hyperbolic of me.
By "full gigabit", I don't mean "exactly 1Gbps", but I'm easily able to reach the same speed to an external network as I'm able to obtain within my ISP's network.
For example right now if I run a speedtest to my ISP's Speedtest.net server, I see 820Mbps. If I run an iperf3 test to my Feralhosting server, I see 820Mbps. If I run a iperf3 test to my Hetzner server, I see 894Mbps.
It's not technically right at the 1Gbps that I pay for but it's close enough that I'm generally happy.
The only time I've ever maxed it out is with five torrents running at once, and that only lasts a second or two, because then they're done. And we're not a light usage household. It's pretty common for us to have three or four streams all running at 1080 at the same time, plus other big downloads and videoconferencing. One main limiting factor is that I've never seen single service provider get close to gigabit speed (like updates from Apple or Sony for example). It has to be a swarm to get even close.
I'm not sure what I'd do with 2Gbps. The rest of the internet just isn't there to support fully utilizing that connection.