The release and tweak model works well for web apps -- today. Because there is no real review model for web apps.

Mobile apps are a lot more like movies. Opening weekend means a LOT. If you are weak out the gate, you'll have bad reviews. When you update, no one will care, because not many people will buy the updated app because of all the one-star reviews.

The only time this doesn't apply is if you a huge built in userbase like Facebook, where even with bad reviews, people will still get the updated version of the app.

It's very, very true that you need to be solid out of the gate on Android OR iPhone. Android's app rankings, in particular, seem to be tuned to give an advantage to new apps, so apps that get good ratings and a bunch of downloads out of the gate can potentially place.

Once an app is a month or two old, even if it's well rated and doing decent, it can crash in the rankings and get buried under thousands of other apps, even if it has a lot of enthusiastic fans. And it seems like this happens simply if people don't download it ENOUGH -- if it loses momentum, you're toast.