[regecks]

Maybe in "fat" language runtimes this is a problem (Ruby, Java, Python etc).

In Go, requests are a single goroutine, dirt cheap (no problem with a single CPU). To me, this type of work is where Go excels.

I used SSE (not quite long polling but I think it has the same implications as far as this discussion goes) back in Go 1.3 days (so GOMAXPROCS=1) to write metrics to 100<n<1000 clients and the process barely registered CPU or memory usage. No lock problems either (copying metric values over channels).

As far as complexity .. well, sure, if you fuck up the design or use the wrong tool for the job you'll have problems.