In the past, most Windows Tablet PCs had digital pens and touch was added as an option relatively recently thanks to the popularity of the iPad and touch screen phones. With Windows 8 tablets, it's reversed: you get touch, but less often a digital pen and dual digitizer. So you're right, the Yoga and some other upcoming products don't offer a digital pen, which is a shame for artists and note-takers. There will be some models that do offer that feature, and Lenovo's own ThinkPad X230t now ships with Windows 8 and has the dual digitizer option. It's a lovely convertible with a center swivel hinge.
Here's our review of the X230 (minus tablet feature) so you can get an idea of the machine: http://www.mobiletechreview.com/notebooks/Lenovo-ThinkPad-X230.htm .