How I Met Your Mother is responsible for NPH's career resurgence. Yes, he had success before then, but Barney Stinson is what made him a household name. How I Met Your Mother was on CBS for 9 years and was watched by millions of people. Jesse Tyler Ferguson doesn't have the same kind of name recognition as Neil, but few do.
From what I remember, the set was just him sitting at a basement office desk fielding phone call after phone call. Whether or not it will fill the theatre (which I, too, think is big for this show), it's a great show and I will be revisiting.