Summary: I've had this phone since October 2007, and i bought it second hand. I have only had one problem so far - and that was because i had it unlocked, occasionally it rejects my sim card, but that is solved by a simple turn off and back on again. Design: The only fault for me is the size, its chunkier than my SPV C500 was, so sometimes at football matches i have a bit of a problem. The keyboard is great, the buttons on it are perfect size for typing.
Summary: Windows mobile is powerful and extensible, but out of the box for a phone or even PDA-based user it can be a bit difficult to use. Microsoft have got to work harder to get up with competition such as other PDA/phone built-in applications. That said, the sync with Outlook and Exchange is excellent and the exec fits in to that laptop on the move idea with out all the luggage!
Pros: Keyboard, Windows/Outlook sync, Wi-Fi, Media player, voice-activated dialling, miniSD for media and files, GPRS for mobile based surfing.
Cons: Slowish CPU and/or short on internal memory. Slow O2 software.
Summary: Just replaced a treo 650 with the O2 XDA Mini S. As a Mac user, I've always leaned towards Palm-based phones as they're easy to sync with Mac OS X. However, combining this phone with 'missing sync' software (about £20) was a breeze - first time sync, no problems. It'll also 'mount' the phone on the Mac desktop for access to my documents etc. So far, very impressive and already knocking the socks off the Treo 650.
Summary: I have never gone more than 3 weeks without either the phone doing a hard reset itself and wiping all my data and software, or me having to do a hard reset because the software became corrupt and only the essential functions would work (this doesn't include the phone). On top of this I would say that I have to soft reset it at least every 2 days and the battery life is poor, meaning you have to keep it constantly on charge.
Summary: The O2 XDA Mini S is in short brilliant. Its new operating system is its core feature, which blows Palm away. The keyboard is extremely useful and makes text-messaging, MSN, email and data-entry actually viable on a handheld. The downsides can be easily rectified without significant extra cost: the slight lack of processing grunt can be offset by software utilities and the immediate removal of O2's 'active interface'.
Pros: Instant, out-of-the-box functionality; Wi-Fi; intuitive, powerful operating system; wealth of features; hi-performance after O2 'software' removal
Cons: apparent slight lack of built-in memory (dependance on new SD-mini cards),
Summary: All round good phone/PDA. Was initially concerned about the O2 ROM as I had heard that there were bugs which cause the device to crash. However I think that there is a new ROM which is installed, my device has no problem. It works well, TomTom works too (with Bluetooth GPS reciever)! Brilliant Wi-Fi. Reasonable battery life. Using the device to call and text does take some getting used to, but it's not a problem. All round brilliant device...
Pros: Most of it
Cons: Whilst listening to MP3's the keypad and screen both can't be turned off, using more power.
Summary: In theory, this looks as though it has everything I want, but using it day-to-day has been a nightmare. It's very slow and crashes frequently, especially if you have more than one app running (and they don't close when you think they have). I haven't installed anything funny or done anything particularly intensive, just looking at emails, web, calendar etc. And it's not just me, my two colleagues had exactly the same problem.