Got this from a wholesaler direct for around $800 AUD.  This is the thinest smartphone available currently beating the Dopods (Very popular in Asian acountries especially Singapore) or O2.

While this may not be your ideal smartphone, X500 has a full range of functions such as WiFi, GPS, and a responsive Samsung 400mhz software.  It had been reviewed elsewhere, X500 is more responsive than the Dopod and as I have tested it, I must say it is very responsive.  A slight delay from time depending on the application used but overall, it is very good especially when paired with TomTom Navigation.   The delay may be up to 15 seconds to retrieve GPS which is by far the one of the most responsive unit I have seen.

Everything else worked as intended but it's is a good idea to switch on the Error reporting to find out what task was done when error occur.

The WiFi function worked well with SJPhone (freeware) to be used with a VoIP account with your VSP (VoIP Service Provider).  You can set up different accounts (if you have multiple VSP) and choose whichever account to make outcall.  The downside of this (software related rather) is the lacks of:

1) Incoming DID (VoIP number)
2) Poor sound quality
3) No integration of address book (which means I have to retype them manually)

Overall I would rate this smartphone 9/10.