HTC's commitment to Windows Mobile and its own TouchFLO 3D enhancements has been dogged to say the least. After its disastrous debut with the first Touch Diamond, when the software clearly wasn't ready, we'd have forgiven it for throwing in the towel and dumping Microsoft's tottering phone OS altogether.
Bravely, however, it has kept on banging away, resulting in a well-deserved PC Authority Labs win for its Touch HD at the back end of 2008.
The Touch Diamond2 heralds yet another significant step forward for TouchFLO 3D - and even in the pre-production implementation we had on our test phone, it marks a significant improvement on all that have gone before it.
First, though, let's focus on the hardware. For although the Touch Diamond2 hasn't seen much of an overhaul from a platform point of view - it still relies on the same 528MHz Qualcomm MSM7200A chip as its predecessor, still boasts A-GPS, Bluetooth 2 (with A2DP), an FM radio tuner and a front-facing VGA video call camera - there's been plenty of change elsewhere.
Most noticeably, the faceted back that gave the original Diamond its name has been dropped and replaced by a large expanse of flat, glossy black plastic. Owners didn't like the fact that it wobbled on a flat surface when they tapped away at the screen.
The Diamond2 is also a chunkier phone than its forebear at 53 x 108 x 14mm, and it's 8g heavier too. No longer does it come with as much built-in storage: the original boasted 4GB, while this model has an eighth as much.
And we were disappointed to see that, unlike the Touch HD, this phone retains HTC's annoying proprietary audio output arrangement - you have to buy an adapter to connect your own headphones via the phone's mini-USB socket.
Fortunately, the Diamond2 is, in every other respect, a superior product. A larger 3.2in screen more than makes up for the added bulk, and that extra size has also allowed HTC to squeeze in more pixels - a 480 x 800 resolution is the same as the Touch HD's. Its extra real-estate benefits web browsing no end, with headlines and sometimes even smaller text viewable when zoomed out.
We're also much happier with the overall design of the Diamond2; it feels more expensive, with the main button panel beneath the screen finished in brushed aluminium rather than tacky plastic. In conjunction with the touch-sensitive Zoom Bar between it and the screen above, it makes this phone much less of a faff and fiddle to use.
And there's more: the camera has seen a boost to 5 megapixels (it's still no replacement for a proper camera, though), there's now memory expansion via a microSD slot, and the battery itself is also much larger: the Diamond featured a wimpy 900mAh lithium ion unit, the Diamond2's is 1100mAh.
That may not sound like much, but in our real-world tests the Diamond2 was able to offer a far more useful lifetime of 169 hours, compared to the 52 hours of the Diamond.
HTC's changes to TouchFLO 3D are the icing on the cake. It feels snappier than previous versions, there are noticeably fewer pauses, and it responded to screen taps in what felt like much more of a "real time" fashion.
The depth of the TouchFLO skin is deeper too.
Where before you'd have to reach for the stylus as soon as you wanted to add or edit a contact, or view the calendar screen, you're now shielded from the ugliness of Windows Mobile (note it's still version 6.1) at most turns. Even the calculator and clock/alarm screens have been given a lick of gloss.
Don't be fooled by the new "push" internet feature, though. This may promise offline browsing, but is limited to a paltry four pages.
Most of the changes are welcome, though, and they go far enough that you'll rarely see the underlying operating system - the sort of overhaul that Windows Mobile has been crying out for for years now. There's still the odd hole here and there, but these are few and far between for day-to-day use.
The onscreen numeric keypad has also been improved, with a far more sensible selection of context-sensitive configurations and layouts.
However, the Qwerty keyboard that appears in landscape mode is fiddly at this screen size, and the two-letter-per-key BlackBerry Pearl-style layout has mysteriously disappeared; if easy, quick texting is your priority, there are better phones around, notably the iPhone and HTC's own Touch Pro and Touch HD models.
HTC's efforts are, however, enough to turn what was a disappointing phone into a far more usable one, with the battery life, improvements to TouchFLO 3D, and the superb screen the highlights.
Despite the slightly fiddly text entry it's more pocketable than the Touch HD, and this means it just about replaces it in our affections. But with HTC's second Android phone (opposite), and a new iPhone too, we're not sure how long we're going to be able to recommend Windows Mobile phones such as this for.