Little bit slower in my opinion. But are you racing people to work? So, does it REALLY matter? Sure it might be a bit more fun riding with less drag, but wind direction makes a lot more of a difference than my IGH.

5th gear on my IGH is straight through. I can tell when I am in the indirect gears, except the highest gear. 6 and 7 are quite noisy on my bike. The amount of noise hasn't really changed over the miles. I suppose the REDLINE version of the Nexus 8 would be smoother and quieter.
I have >10,000 miles on my Nexus8 IGH. I do nearly no maintenance on this bike. OK, maybe oil the chain a couple of times a year. I have steel sprockets. The only work I've done on my glorified beach cruiser Bianchi Milano is a change of tires, handful of tubes and infrequent chain lubrication. I LOVE the no maintenance aspect of this bike and the IGH has a lot to do with that. I also have a rear roller brake that isn't as powerful as a regular rim brakes, but it works the same in rain, snow or shine. I rarely pull the front rim brake on this bike. I imagine the roller brake will last about forever too.

For a commuter? I think IGH is the way to go. No maintenance. Inconsequential sprocket and chain wear means more time riding and less time wrenching. Add a roller brake for all weather braking without maintenance too.
If you are like RickyBobby and wanna go fast, IGH isn't the best. IGH is heavier, has more drag, and doesn't cost less than a traditional multigear set-up. Roller brakes are too heavy for racers too.