You can only use it as a remote control: it means that you can only control locos, switches etc that are set in your CS2

Oh man, what can the Main Station app do! WOW!
I use it a lot. You connect a Wi-Fi router to the CS2 (ensure that you have the recent updates), turn on your app after making sure that the iPad is connected to your Wi-Fi, wait a minute to connect, and then let the fun begin.

You have 4 screens, 2 of which are customizable and saved.
Remember, the Main Station App will reproduce what you have on your CS2. Nothing more, except quicker screen access.

Each screen will have 4 modules and when you hit the (i) on each module, you have a choice of 2 vertical lok controller, 1 speedometer lok controller, keyboard for switches, etc., memory screen, layout, and general information.

You select the lok by touching the lok icon and scrolling to a new lok. All the function symbols will come up. So if you have all your modules seclected to 2 vertical lok controllers, you can control 8 loks with one screen!

The keyboard and memory is just like the CS2, but easier to scroll through and will only show pages that have been set-up.
e.g., I have switch address of 11,12 & 13 for Marklin switches and 200 and 201 for Viessmann 4554 slo-mo swiches. The keyboard display on Main Station only shows tab 1, 2 and 13; easier to go to the needed tabs with Main Station as compared to CS2.

I do not have any Memeory set up yet.

The layout works great!. You can pinch to zoom in and out to get to those switches. I rairly use the keyboard after I set up my layout. You can pull up whatever layout you have in the CS2 or scroll through the large layout.

There is a devices module that displayes the current, voltage and temp of the CS2 and MS too.

And finally there is a clock to help keep track of time while you are having fun!

Some things to keep in mind. The app will change to portait mode and give you 2 larger modules as opposed to the 4.
If you have a timed lock-out, you will have to wait to re-establish contact again. If this is annoying, you can disable the inactive lock-down timer of the iPad.

I had a lot of fun using this at the train show as it allows me to mingle with the crowd while running the trains. No one in NA has this feature and there is good jelousy generated.
However, this has been rare, but due to the fact that I had my iPad lock down and requireing password to unlock, I had to delete the CS2 memory in the iPad and re-establish a connection on occation. It may require a restart of the CS2 to restart the communication. This is not a fault of the app in my mind.

If you have a larger layout and an iPad, get the app for the small amount that it costs, the freedom is worth every penny. I also use this in conjuction with my iPod and Mobile Station app, althought the new Touch Cab has more versatility and more robust.

Wow. Some great info there from you all. Thanks so much! On the back of it, I've just downloaded it. Sounds like a bargain for 8 quid.