They were either bad apps in general or were potentially nice phone-sized apps with no optimisation done for tablets. When I say optimisation I'm referring to both the UI layout and the general rendering performance. For some reason (I'm not an android dev) certain apps have performance issues that scale with your pixel count (I guess they are hand-rendering things themselves and simply Doing It Wrong) and make them unusable.

I can't remember which though, so I'll install your top two when I get home (~8-10hrs) and report back.