Hertford Astronomy Group
I use GoSkyWatchP (GoSkyWatch Planetarium). I like it.
The free version (which I use) has a band of advertising along the bottom of the screen. This is annoying but the kind of iPad cover I have covers it.
The refresh rate is higher than some other free APPs I've tried, so star movement is smoother.
The free version is given 4 stars by users; the pay version (£2.99) is given 5 stars by users, on App Store.