I've been using the Dual for over a month now. I'm used to a full keyboard WinMobile phone like the Treo750. The 20 key takes some getting used to but the software works pretty well. It is a pain to insert proper names as it keeps suggesting bizarre alternatives. Those people used to a 20-key should have no issues. If they made this with a full Blackberry/Treo keyboard and no slideout, I'd prefer it...
The phone is functional and works well on my ATT network - I've had no issues with phone or data connection (see below for device issues).
Htc incorporated many "neat" software add-ons that improve upon the standard Mobile 6.1. While they make the device cooler (if a WinMobile phone can be cool) than standard Winmobile devices, I don't believe that they are enough to recommend buying the phone over another manufacturer's though.
My only complaint is a massive one. I've had issues with the phone resetting itself everytime I forget to charge it. It falls into a "hard reset" where I must tap the screen, set the time zone and time, and re-insert all data and personalizations. It does this when the battery drains due me not charging it for one reason or another. While I understand that the battery will lose its charge, the phone shouldn't lose all data when this (inevitably) happens. I should be able to plug it in, recharge it and use it. Nope. Dead. Hello! I'm a new phone. Pleased to meet you. Please input all preferences and data.
HTC cannot identify my eXpansys-bought phone since it is not bought from its "official" sales channel in the USA - Bestbuy. This, after providing them with the serial number... I cannot upgrade the ROM (presumably ever) because of this.
Even though the phone and software work fine when not dead, I cannot recommend buying this phone from this seller. Buy another brand phone or buy HTC from the official channel.