Grepping the source code of Unity 3.4.1 indicates that Windows 7's multi-touch/gesture support is not currently used. The touchscreen support mentioned is a bit misleading - it appears to be single input mouse emulated only.

Unity 3.5 appears to handle device hotswapping, but does not appear to add any Windows 7 Touch API support.

uniTUIO will get you what you need until Unity adds much needed built-in support. You will need to register to gain access to the uniTUIO side to download it but it should be open for development use. It was a little bit of a pain to get going with but we were able to build an awesome game for a giant 12 point touch screen with it.

Windows 7 (at least i have a machine that has Windows 7 that) does support multitouch. However, most traditional PCs (at this time) do not support multitouch. You may want to go with iOS, Android, or Windows Phone, or wait until Windows 8 comes out.

OEMs will be getting Windows 8 later this year so we will probably see an omega version early next year. You can get a beta version of Windows 8 at http://windows.microsoft.com/en-US/windows-8/consumer-preview.

Is there any update on the situation? I would like to use multitouch-gestures in Windows7-projects as well!

If you are still interested in multitouch in Windows 7, we have released a native solution, which does not requires TUIO or any other external program. http://forum.unity3d.com/threads/152685-RELEASED-Windows-7-multitouch