$20 Fujistsu Stylus with Thinkpad Tablet
I just wanted to share a tip I ran across while setting up a thinkpad tablet to demo. N-Trig styluses all seem to be cross compatible, meaning you can use a pen from a Fujitsu Q550 or HTC Flyer etc with the Thinkpad tablet. I bought a Fujitsu stylus with mine because it was < $25 shipped, and the Lenovo part was backordered at the time. To my surprise, not only did the Fujitsu stylus (part number FPCPN36AP) work with Lenovo, but it actually fit almost perfectly in the pen silo.
Today a received the official Lenovo pen (part number 0A33887), and compared the two. Both came is almost identical packaging, with the same accessories (2 spare tips, a AAAA battery, and an identical tether). The only differences are a slight indentation near the tip of the Lenovo pen which seems to help it grip when stored in the tablet, and the fact that the Lenovo pen's large red "eraser" end makes it easier to pull out of the tablet with a fingernail etc. I tended to use the tether string from the Fujistu pen to pull it out from the silo. Other than that, the two pens share roughly identical dimensions and build (see the attached pictures to compare). The button on the Lenovo pen is firmer, and has a shorter travel, leading to less accidental pushes.
The HTC Flyer pen is good to know about, as it can be picked-up locally at pretty much any Best Buy if you lose your stylus and need a replacement quickly. It was a ridiculous $80 last I looked, but it's a more reasonable option at $40 as of now (though the link on the best buy web page seems to be gone). It also has a second "erase" button, but I don't know if it's active in the Lenovo software.
I wanted to leave this here, as I hadn't seen this documented anywhere when I was looking for a stylus. I'd be curious to know if someone tries the HTC pen, or knows of other N-Trig styli.