Apparently he wasn't going to sign with the Islanders. Either they think what they have is better or Niemi didn't want to sign with them, or a combination of both. So the Islanders got what they could for him before he re-entered the NHL draft and/or went back to Finland. I understand the Rangers have already signed him to an entry-level contract.
He needs another year in the WHL but will be coached again by Lorne Molleken who has a good track record with young defensemen (Jackman, Exelby and some kid named Mike Green). I think getting a 19 year old with his size and talent base with the upside is well worth the 6th rounder the Rangers gave up. Some say he's not strong defensively but his +/- lately says otherwise. His offensive skills is what sets him apart. One of the hardest shots around.
"This has been a great day for me," Niemi said in a phone interview from Finland on Tuesday night. "This is something that I've been looking forward to for years -- to get a chance to be part of an NHL organization, and I couldn't be more happy right now. I'm just looking forward to joining the team and meeting all the guys." http://rangers.nhl.com/club/news.htm?id=530301
Did he not consider the Islanders an NHL organization? (Sorry Isles fans, couldn't resist)