It really depends - there's been some posts on HN criticising the freemium approach:
- http://www.tylernichols.com/web-development/i-am-done-with-t...
- http://blog.rapportive.com/is-freemium-right-for-you
When building AppCodes I decided to sacrifice the learning curve for the ease of use once the tool is understood.
This kinds of products don't work well when published with freemimum plans - people don't try to understand the product, skip the tutorials, sign up for free, spend 5 seconds evaluating the tool, and unless the learning curve is very calm - leave.
What I prefer is for people to take a while and make sure they understand the ASO process ( http://www.slideshare.net/kolinko/appcodes-app-store-marketi... ), and then - once signed up, to spend a while learning the tool. The expectation is that the ones that go through this will get a better experience afterwards. The ones that won't - there's a no-questions asked refund :)
Another thing with freemium is that it works best with products that people use consistently for months and years. While this might be the case for web SEO or for app sales tracking, in case of App Store SEO it really isn't. You want to spend 3-5 months setting up your position, and once it's all set and you can forget about it.
If I was running a freemium service, I'd have to find some tricks to keep bringing people back. I'd also be more inclined to gear the service towards the app developers with more than one app - because only those devs would bring in the profit.
I don't track our competition too closely, but the last time I checked, that was what they were doing. Publishing charts of your position, and sending you e-mails of your daily rankings (even though rankings in the app store rarely ever change), and moving towards Enterprise customers. They also tend to deliver an interface that's easy to learn, but not that effective really (e.g. they don't bother distinguishing between iTunes keywords, and App Store search phrases).
At least that was the case with the ones I checked...
If you disagree, I'd greatly appreciate a reply :)