Many of the ones that actually have apps treat them more like news feeds than new ways of rendering their magazine (e.g,. see the Sports Illustrated app, for example). Hey, I've got plenty of news apps already. If I'm taking the time to download your app it's because I want the magazine content, not another news feed.
I shouldn't complain because most of the magazine apps out there are free, right? Wrong! I'll pay a monthly subscription price for this app if you'll just get me the content I want.
Here's a good example: My BusinessWeek print subscription just lapsed. I tried the Kindle version but was underwhelmed thanks to missing content and the awful way magazines are rendered on it. I can either renew the print subscription for $40 or go with the lesser Kindle edition at $2.49/month, or roughly $30/year. I'm opting for the Kindle version, but only because I can stop it at any time. I'd pay more than $2.50/month for a great iPhone app version though.
Of course we've all heard about a number of new and interesting devices on the horizon, several of which sound like a good fit for magazines. That's wonderful for everyone with a few hundred bucks burning a hole in their pockets, but why not take advantage of the platform that's already in millions of peoples hands?!