originalsnuffy: Betaplayer has had MP4 support for some time, just don't use the AVC profiles in Recode and you should be fine. Don't ignore the Nero Digital Mobile player as it may be a little confusing at first but being a commercial product (free if you have bought Nero 6 Reloaded) a lot of time is being spent on improving it.
KeithGP: The frame size is set to a maximum of 352x288 because you are using the "Portable" profile, if you use "Standard" then you can use frame sizes up to 720x576. This does mean you can end up with videos bigger than the size of your screen which will mean additional work for the resizer when you play it back.
For specific questions on Nero Digital, the
Doom9.org Forum is the place to go, most of the developers post there and the users are extremely knowledgeable.