[UPDATE: Since we posted this review, HTC have released a ROM update which alleviates the speed problems with the Touch Diamond.]

When weighing up whether to buy the HTC Touch Diamond, we’d suggest you keep one dominant image in your mind: a set of old-fashioned scales. On the left, we’ll put the bad stuff. And on the right, we’ll throw in all the good. Very little about this product falls in between.

Top of the bad list has to be: it isn’t the Apple iPhone. This wouldn’t matter except it’s clear this is what the Touch Diamond is trying to be.

For starters, there’s the way it tries to mimic the momentum idea: drag down on the screen to browse through your contacts, and it keeps on going for a few cycles more.

On the iPhone, it works. On the Touch Diamond, it’s irritating: drag and everything moves too fast, or doesn’t move at all because your finger is in slightly the wrong place.

The TouchFLO 3D interface – the touch-based layer HTC plasters over Windows Mobile – owes more than a little to Apple too. Everything’s animated and whizzy and 3D, which would be fine if it weren’t for the Diamond’s second problem: it’s slow.

To cycle between Internet and Mail, you swish your finger from left to right on the screen. And then you wait. Has it worked? You don’t know until half a second later, when TouchFLO animates the swish.

You can increase the speed a little in the Advanced menu settings, but at the expense of battery life and not enough for our liking.

Battery life borders on disappointing. At a stretch, you can get three days’ use out of the Touch Diamond, and for some that’s enough. But for just as many people, it will be disappointing: no-one wants to hold back on what they do of a weekend just so they can eke out a bit more battery. We’re also unconvinced by the fiddly button system.

Thankfully, there are several things we really like.

The web browser is based on Opera Mobile 9.5 and coupled with the excellent 480 x 640 resolution screen, it makes even mobile-unfriendly sites easy to navigate, helped by HSDPA support.

We’re also fans of the built-in accelerometer, which means the Touch Diamond knows how you’re holding it – in portrait or landscape mode, for instance. The hardware design is another plus: at just 110g you won’t notice this phone in your pocket. There’s even a GPS receiver.

In many ways, we like the TouchFLO 3D interface. Being able to launch a web browser, email, photos and videos and music without being dumped back into Windows Mobile 6.1 is a big plus. But overall, the bad outweighs the good.