If you don't know who Tom Kalmaku is, see Casting Tom Kalmaku, Review of GREEN LANTERN: LEGACY, and The Origin of Tom Kalmaku.
What do I think of this? On the minus side, Beach isn't Inuit. No doubt the filmmakers made little or no effort to find an Inuit actor. This seems to be standard operating procedure in Hollywood.
Also, Beach is four years older than Ryan Reynolds, who is playing Green Lantern. I'd say Tom Kalmaku should be in his mid- to late 20s and 5'6" or thereabouts, not 37 and 5'11" plus. That's the way he was in the original comic books.
On the plus side, Beach is a Canadian Native, which puts him closer to the Inuit than most actors. He looks more Inuit than many Native actors--certainly more than, say, Wes Studi or Russell Means. Beach's boyish enthusiasm matches Kalmaku's boyish enthusiasm for his pal Green Lantern, so he could be a good fit.
Most of all, thank God the filmmakers didn't offer the job to Johnny Depp, Taylor Lautner, or another pseudo-Indian actor. For once an important Native role goes to a Native.
If casting Depp as an "Eskimo" sounds odd, consider this. Depp the 1/8th Eastern Cherokee is no more related to Tonto the Apache than he is to Tom Kalmaku the Inuk (singular of Inuit). In fact, I'd guess the Apache people--of Athabascan stock from the far north--are more closely related to the Inuit than they are to the Cherokee.
For more on the subject, see The Best Indian Movies.