HTC HD7 / HD7S

I think that has something to do with the hardware specs mandated by Microsoft. There's a "chassis" spec that Microsoft dictates, which is designed to:

1. Set minimum specs and features, so all Windows Phone devices deliver a "premium" experience.

2. Simplify the platform by standardizing the hardware to some degree.

That second one is where is get tricky. In theory, it's a good thing, but it can have negative consequences as well.

You see, a big part of what slowed down Microsoft Windows Mobile (5 - 6.5) development toward the end was that they had to support a large number of different chipsets, screen sizes, etc. Plus each carrier had their own customizations and testing process. It really bogged things down. Standardizing on exactly one Qualcomm Snapdragon chipset for all Windows Phone 7 devices simplifies things greatly. If they can keep the number of hardware variations under control like this going forward, it should mean dramatically faster improvements to Windows Phone as they have few hardware variations to develop for and test against.

Unfortunately... since Windows Phone 7 was a big undertaking, clearly requiring the coordination of a huge number of hardware, software, and carrier partners... the point when they had to "freeze" the hardware spec was last year. At that point, the best available chips were last year's Snapdragon chipsets. I think those don't support HSPA+, only the new Snapdragons this year do.