iDisplay is a really cool app for iPad, that until recently was very awful. The problem was not with the App itself, but with the supporting desktop application. iDisplay lets you use your iPad (or iPhone, if you can think of a use for that) as a Wifi connected second monitor. As I use my laptop for photo editing on location, having the ipad as a tablet for my toolbars with a full screen photo on the desktop is sort of a holy grail for me, so when I first paid the £5 I was pretty excited. I first downloaded iDisplay about a year ago when I fist got my iPad, and the App had many issues. Firstly, the App had serious latency issues causing a laggy response. It was too frustrating to use for any serious work. Secondly, the supporting desktop app was appalling, there was no way of disabling the secondary monitor when your iPad was switched off, so I permanently had 9" of dead space to the left of my screen, which had a secondary effect of disabling my Hot Corners. Delete.
I decided to give the app a second punt, as a few updates have passed. The Desktop client is remarkably improved. A Windows version is available now for all you Microsoft sufferers , (as is an Android version) but more importantly, When you shut down the iDisplay client, the external monitor dissapears, as you would have expected all along. The latency issues are greatly reduced. A bit more speed would be nice, but its quite useable now.
The App itself is greatly improved also. One problem was always due to the iPads pixel density being higher than the MacBook Pros screen meant photoshop tool panels were too small to use. Now the app allows you to pinch to zoom around your desktop, enlarging the smaller panels to a useable size. The app will now auto rotate from landscape to portrait, which is also a great benifit.
The App seems very useable now. I feel I was treated as a beta tester initially rather than a paying customer. I am yet to use it in anger on an assignment, but it is very promising so far. The review score on the Appstore is very bad due to how crappy the old client was, this score does not reflect the new apps abilities.