I'm having the same issue. At first I thought it was because I hadn't updated my iOS (from 4 to 5), however, a friend of mine has updated her iPhone and iPad, and she is still getting the same "This App is Incompatible with this iPhone/iPad". Btw, there are several other Apps now displaying this message (e.g. Accuweather). My thought is, that perhaps these lateest updates require BOTH iOS 5 AND iCloud in order for the updates to be applied. I'm curious if anyone else has thoughts on this issue or my hypothesis?
I am getting this same error message for Pages on my iPhone 4 with iOS 4.3.5 installed.
An even bigger concern for me, it seems, is that the error prevents any of my other apps from updating via "Update All". So, I've had to go through them manually one-at-a-time, to update the other apps. This is a pretty glaring error... who is doing to approval for app updates that come from Apple apps?? Come on, Apple, I expect you to be better than this.
Update: This is also true for the App "AccuWeather for iPhone" and "Numbers".
Clearly, this requires that the App Store app get updated not to present these updates to iOS 4 users.
The update for the Pages App which I already have and use on my iPad (1) won't download. I keep getting this message: "This App is Incompatible with This iPad".
This makes NO sense.
Pages / Numbers / Keynote v1.5 will only run on iOS5 while v1.4 runs at iOS4.x.
v1.5 introduces iCloud options that are only useable in iOS5, that's why.
More and more apps will go this route. Sketchbook Pro Mobile for example is now also iOS5 only for the same reasons.
Also there are now Apps in the Store that require the newest iPhone4S.
We simply must read the system requirements in iTunes before we hit the download or update button.
Here's the answer - I needed to update my iOS to iOS5. Simple fix - then the Pages App update would be compatible.
However, before updating to iOS5, I wanted to back up & sync first. I did this.
Then I chose to update to iOS5 - well, iTunes needed to back up my entire iPad content on the computer and my hard drive was pretty full (and my iPad had too much on it). So I reduced what was on the iPad (and changed by Sync parameters) and I went through my hard drive and cleaned out a lot of stuff.
THEN, when I had plenty of time - like all afternoon - I updated the iOS. good thing I allowed all afternoon because the entire process took close to 2 hours.
But now it's done and I have iOS5 and my Pages App is happy and all is well. For now.