I'm not sure what a "cheat grass" is, but P.v. 'Shenandoah' is far from invasive. In your zone, it should be very well behaved. You're in the north end of it's hardiness range, so it isn't likely to set viable seed, or reproduce in any other fashion.

I have a small clump from a small division about 2 years ago, and it's doing just fine. It's only about 18" tall right now, and looks like it may hit 30" this year. The clump is tight and upright and has gorgeous coloration.

I just potted up 5 more of them from the Park's Wholesale clearance sale. They'll probably go into the ground in late summer.

Agree with donn. I have a 'shenendoah' that is in its second year. About 2ft tall right now, rather tight clump with the outer reaches of foliage "dangling" downward. Some of the tips have reddish tinge to them. The plant is probably about 1-1 1/2ft in width.
I see no signs of "volunteers".

I love this grass ...
I agree with both of the previous posts, I have seen no sign of invasiveness.
I have had one plant for five years, and had to move it twice because neighbors outgrew it. It doesn't seem to spread fast, but forms a very tight stand.
My second plant is two years old, receives more direct sun, and doesn't have the dark foliage color of the older plant.
I started two new Shenandoah this year using divisions from the younger plant and they have taken off rapidly.

Your friend is ill-informed. "Cheat grass" is Bromus tectorum, an annual running grass and is in no way related to Panicum virgatum, a perennial clumper. IME, like the other posters, panicum (switch grass) is very well behaved and not the slightest bit aggressive, although in the right conditions (generally, rather moist soils) it can spread rhizomatously, but typically not enough to be considered a problem. Self-seeding is usually minimal as well.

Yes , that is well said . Hurray for 'Shenandoah' !

About 'shenendoah'. I have seen pictures of this grass (in a couple of different catalogs) where almost the whole plant is a purplish-red.

Now, while I still like my 'shenendoah', my grass is very green with a few of the "tips" turning that purplish-red hue. Curious as to know what your experiences are as far as the coloration of this plant. Is your plant nearly all colored purplish-red? Or, is it more similar to the one I have?

My 2 year-old plant started green, and is getting more red highlights as the season goes on. It's supposed to gain more coloration through the summer, and become mostly burgundy by fall. Since you're at the cold end of it's hardiness range, I would expect the coloration to come along later in the season than in my zone. I have 10 new plants, growing from 3" pots, and they have no sign of red at all.

Thanks donn,
I took a close look at mine the other day. I noticed more "tips" are beginning to show the (I'll call it burgundy) color.