[HD2 General] maati:
Some general thoughts, in addition to my answer above:

The hardware of the HD2 is better, hands down. However, the software is quite different. I think none of the operating systems, Windows Mobile or iPhone OS, is better or worse, but they are very different and have very different strenghts and weaknesses.

I can give you some thoughts that may help you decide:

The iPhone is very easy to use, fluid and most of the time, 'just works'. However, this comes at a price: It is also very limited, in order to achieve its ease of use.

As long as you don't reach the limits, you're fine.

But when you reach the limits

(e.g. you want to have information on the home screen, you want to multitask, send something via Bluetooth, use it as USB storage, costumise ringtones and so on...)

then things get complicated on the iPhone. You either can't do something at all, or you need to hack/jailbreak it or find workarounds for the shortcomings.

With Windows Mobile, you get everything out of the box. It can do pretty much everything and has all the basic and advanced features that the iPhone lacks.

However, just like the iPhone's ease of use, Windows Mobile's feature-richness comes at a price as well: It definitely is more complicated and doesn't always work instantly, if you want to install/change something.

Sense tries to make the basic things as easy to use as on the iPhone, and I have to say it does that quite well. But it's still not THAT easy.

On the other hand, if you want to go beyond the limits that Apple set on the iPhone, things often get MUCH more complicated than they are on Windows Mobile.

Conclusion:

If you don't reach the limits of your iPhone, i.e. if you're not missing anything that the iPhone can't do, then it will probably the better device for you, because then it's more easy to use and 'just works' for you.

If, however, you miss a bunch of features and you try to work around them on the iPhone (e.g. by jailbreaking it), then a Windows Mobile device, particulary the HTC HD2, is probably the better choice, because though not everything is as easy, you get everything out of the box. And you also get the better hardware.

The HTC HD2 also has a special place among the Windows Phones. Sense/TouchFlo has evolved over time and now the basic things (i.e. everything that the iPhone can do) are almost as easy on the HD2.

There are still exceptions, like installing software, but it has come so close that I

personally think that the HD2 is the better choice for almost everyone, except for those who really never reach the limits of the iPhone.

Because, for giving up a bit of ease of use, you get tons of additional features, as well as the better hardware:

- 4.3" screen, much better camera, faster processor, more RAM...

- multitasking

- maximum customizability

- no iTunes required, you can connect it as storage device

- file explorer

- better notifications concept

- more professional, customizable home screen

- Bluetooth file transfers

- good Emulators like Morphgear

- and much more

Whether this is enough to make you accept the loss of ease of use compared to the iPhone is your choice.

Previously, the gap in ease of use has been much greater, that means you had to sacrifice a lot more in order to get all the features of Windows Mobile, but with the HD2 HTC has come so close that I think it's really the better choice for lots of people now.

However, everyone still has to decide for him/herself. I hope I could help.