First, the good news: Virtually everything works straight out of the box. There are Windows 7 graphics drivers ready and waiting for most of the machine's hardware, and even drivers for the fingerprint reader and the SD card slot.
Second, the not so good news: Some of HP's built-in tweaks and speciality hardware aren't supported yet, and there's some question over whether they will ever get Windows 7 drivers. That's always a risk when hardware pre-dates an OS. It's certainly a little annoying when the screen won't autorotate, and the slider volume control on the keyboard won't work - but there are workarounds using OS features such as Windows 7's Mobility Center (call it up with Windows-X) which gives you rotation and volume controls.
Third, the better news: You can get all those functions back using the latest versions of the Vista drivers from the HP web site.
So far I've been able to get back rotation and special keys (including the volume slider and mute button), the accelerometer-based hard drive shock protection and control of the WiFi and Bluetooth cards.
You'll need the following SoftPaqs:
SP43616 - HP Quick Launch screen rotation and special keys
SP38424 - hard drive shock protection
SP39734 - WiFi and Bluetooth manager
These will give you most of what you need. Some set up guides suggest using earlier versions of the Quick Launch driver, but this one works well for me.
You'll also find a couple of devices without drivers in Device Manager. These are part of the Intel AMT device management suite, and aren't really necessary for most users. If you do want to get them running you can find the drivers for these in these two SoftPaqs: SP38312 and SP38313.
The installers for these drivers won't run under Windows 7. However the files will unpack into folders under C:\swsetup. In Device Manager right-click on one of the two unsupported devices, and choose "Update Drivers". Choose to install from a local folder (and make sure the "use subfolders" option is selected). Pick C:\swsetup and let Windows install the device driver. Do the same for the other AMT device driver.
And that's everything you need for a fully configured Windows 7 machine.
I found this forum thread very useful when setting up my machine