It has to be said, though, that when using the Guide for navigation we did find the screen to be a bit on the small side. The smartphone only has a 2.8in screen, whereas most sat-navs on the market today have displays that are at least 3.5in in size. It's also annoying that the navigation software can only be used in portrait mode rather than landscape mode, although, to be honest, the display is so small this was probably intentional so that the screen could fit more of the road ahead in. Also the Guide's speaker isn't all that loud so it can sometimes get drowned out by engine noise.
As with most HTC made devices at the moment the Guide is charged via its mini USB port that's located on the bottom of the handset. This also doubles as the headset jack so you can't listen to music while you're charging the phone, but at least you do get a proper wall charger in the box, along with that in-car charger. O2 says the 1100 mAh battery is good for around six hours of talk time and between 300 - 400 hours on standby. In our experience, you'll get around a day and a half's usage out of it before it needs a recharge, which is a bit less than usual for WinMo smartphones. You'll also need to make use of the in-car charger when you're using the navigation software as the GPS chip tends to really hammer the battery.
The XDA Guide is a good smartphone but we're not convinced it's also a great navigation device when used in the car. The small screen and quiet speaker work against it and make us think that O2 should have gone with another, larger touchscreen device from the HTC range for this navigation bundle.