Winsupersite is heavily biased towards whatever MS does and has been for years. Nothing really new there.
He really disliked Windows Mobile, he was even harsher on it than engadget at times.
guess your just unlucky. btw, I've used every version of Windows since 3.1 and I never had random crashes in Windows 95 or 98, I used a Win 98se machine for 5 years without rebooting except to install updates.
On an open platform like Windows or Winmo it's possible to get crappily programmed apps, but that isn't the OS's fault.
You could say it's the fault of the app, but the entire OS shouldn't go down because an app crashed. Windows 9x was always hell for me, but a lot of that was driver issues. XP was a big improvement in stability, and Vista and 7 even more so, in my experience and in Microsoft's own statistics on the issue. Windows Mobile is still a 9x era design in terms of apis, security, and sandboxing. (and the kernel hasn't been updated since 2004, it doesn't even support the latest arm instruction sets so it's less optimized than it could be)
Now that Android has opened itself up to native code, it's increasing its risks, but it has a more modern design. I expect the underlying design of Windows Phone 7 to be better though, just because it provides support for managed C, so native code isn't as necessary.
Anyhow, WinMo is a dead platform. There's likely to be no major improvements for it, and Firefox Mobile and
Flash 10.1 for it have been canceled. It'd be nice if Microsoft had brought the under the hood improvements of windows phone 7 to it, but it doesn't look like they will. Most android phones will get OS updates over time, and the iphone is guaranteed. The HD2 will always be the same as it is, and the lack of a stylus means that many native windows mobile apps don't work well on it anyway. Reviews of it say it makes Windows Mobile much better, by almost entirely hiding it, yet it's horribly unsuited to make use of normal windows mobile programs due to the lack of a stylus.
It sounds like the worst of both worlds. A locked down proprietary OS/interface (the sense UI), on top of windows mobile without providing a stylus.
But the best advice with any purchase, try it out yourself. Tmobile stores should have the HD2 on hand, OP have your girlfriend try it out and see if it meets her needs. You may not be able to find a nexus one, but the droid at a verizon store would be close enough, just ignore the hardware keyboard.
(and if she's on a family plan, she can't get the nexus one anyway, so the choice is between hd2 and the g1)