What we haven't mentioned as yet is the box content, which is actually rather good as you get a multi Voltage charger with adapters for Europe, the UK and the US. Of course it'll work in other countries that use the same type of power plugs as well. It also comes with a USB cradle which has two rear USB ports, one for the charger and one for the sync cable. The 503G can still charge over USB, but this way it doesn't tax the power of your USB ports on your PC.
You also get a headset, but this is quite awful. Luckily the 503G uses a standard 2.5mm headset jack, so it should be easy to find a replacement headset.
So, how to sum it all up? Well, the UBiQUiO 503G is an interesting device which is something of a jack of all trades, but manages quite well to do it all. It comes with a great bundle of bits apart from the headset, although the software bundle isn't anything to write home about. It's got a few minor issues which is something that will hopefully be corrected via a software update, this should be available shortly.
The hardware is very good and overall the 503G is very nippy and felt faster in use than the HTC TyTN, although it should with more memory and a faster CPU. Its small screen and keyboard might not appeal to everyone, but it makes for a slimmer device than those with a pull-out keyboard. There is very little lacking, but there's always the next model to look forward to. Overall, UBiQUiO has done a good job with the 503G.
In terms of availability, don't expect to walk down to your local phone shop and pick one up, as you'll most likely have to order one online. However, it's being sold by Expansys and they have online shops in most of Europe, the US and several Asian countries as well as Australia and New Zealand, so availability shouldn't be a huge issue.
Price wise, you'll find that the 503G costs differently in various countries, but Expansys Taiwan lists it for $679.99 USD with it being $899.95 AUD in Australia. You can buy it in most countries from Expansys.