I've seen reports that the X-Plane android app does not work on all phones, because it uses a graphics set that isn't standard and which some phones does not support (like the new Samsung Wave S II), because it's not part of the official spec for graphics.

For some reason or other the Samsung Galaxy SII is not supported. Maybe it is the Mali-400 GPU. It works great on my HTC Desire HD (Adreno 205 GPU)... not bad for US$4.99... of course if you add all the add-ons planes and scenery it is going to hit US$60. Have a mini review here: X-Plane for Android

I've got it - it's alright.
You're simming on a smartphone at the end of a day. Go in with realistic expectations.

I got my first X-Plane add-on, the F-4 Phantom... my only complaints are:

1) The only cockpit option is the virtual cockpit (no dash);
2) Combat it mandatory unless you select the San Francisco map.

If I decide to fly the Phantom in any other map other than SF, I have to dogfight an enemy plane. It would be preferable if combat was optional even if I selected a different region. It is okay to have a dogfight option for my 0.99 cents, but I think I will stick to non-fighter planes... dogfighting on X-Plane does not feel too "sim" like.