[Windows Phone 7 Q&A, Help & Troubleshooting] GoodDayToDie:
1) WP7 can use your Google contacts, Calendar, and sync your Gmail account just fine. You need to have a Windows Live account, but you don't really ahve to do anything with it. If you already have a Xbox Live account or Zune Tag, just use that. FWIW, I personally really don't like either the Windows Live or Google web interfaces, but prefer Bing over Google for first-try searching (I'll try the other if I don't find what I want right off the bat, but I usually find what I want faster if I start with Bing).

1.1) Be aware that Bing is pretty integrated into Windows Phone, while Google is not. In fact, Google has very few apps for the phone. Although the integration with Google services like Gmail and Calendar is good, others like Talk, Voice, Docs, and G+ is not. Google has (not a huge surprise) shown very little interest in developing apps for WP7.

2) Zune gets updates every now and then. The last was just before Mango came out, call it five or six months ago. It definitely supports Repeat though, both on the phone and on the PC... As for syncing with WP7, it's very good. You can choose what types of media to automatically sync, you can manually sync anything, and yes, things like custom playlists are certainly supported. If you've added a folder to your "Libraries" in Windows, the Zune software will see it and be able to sync it. You can also manually add additional folders.

3) I don't know anything here. There's a "Dock Mode" app on HTC, but as far as I know there's no standard dock interface on WP7. All the phones use MicroUSB, but they don't put the ports in the same place or anything.

4) So far, all updates have been available for all phones. I don't know how long that'll keep up, but Mango isn't even slightly laggy on my first-gen HD7 so I expect it'll remain true for a while. The only reason to wait for a newer phone is if you want new hardware features; the software is almost entirely the same across all phones and all generations. None of that Android fragmentation, where a device may be running an obsolete major version at its release, never be brought fully up to date, and abandoned six months later while there's still a long wait on your contract.

5) WP7 can stream music to A2DP BlueTooth devices, and can use Headset profile BlueTooth as well (of course). It's a little more limited than other smartphones in terms of BlueTooth - no native support for file transfer or BT tethering, for example - but it's generally suficient and MS has added capabilities in previous updates so hopefully that will keep going.

6) So far, no natively WP7 devices can run Android. It's theoretically possible, but you'd need both an unlocked bootloader and a port of Android to the device's hardware. The only phone I know of that can run both WP7 and Android is the HTC HD2, and that actually comes with Windows Mobile, not WP7 *or* Android. It's also a bit old and becoming hard to buy.

7) There are many thousands of free apps, or apps with functional trial versions, in the WP7 Marketplace. That includes games. It's certainly not as vast (yet) as iOS or Android, but those platforms have huge head-starts. It's growing very rapidly. Microsoft has also put some effort into "must-have" apps and games, although generally those end up costing a few dollars. Almost all paid apps have trials, though.