Ooh, thanks for finding that. I'll definitely want to try out the Orenz models and the Uni as well.

I'm also a heavy user of sliding-sleeve mechanical pencils. I prefer metal-bodied ones from the 1970s-80s, but among what is currently available new, I think Orenz are the best.

I have several of all the models, and I prefer the basic model, as it is slim and sturdy. You can get them in 0.2, 0.3, 0.5, and 0.7 mm. I think the 0.2 is not worth it, as it is rather fragile. If you want a really fine line, it's easier to just use a harder lead in a 0.3. The 0.7 is rather pointless, because 0.7 mm lead is so sturdy. The 0.3 is great, as it allows you to press harder and write longer between clicks. I've found them very reliable. I also use the 0.5 for colored leads, which are generally more brittle than graphite leads.

The Uni Kuru Toga gets mixed reviews. It has an auto-advance mechanism that works when you press and lift the tip. The amount of advance is geared for writing with very short strokes, as you do when writing Japanese. It can be awkward for writing cursive. Also, the mechanism rotates the lead, so it's hard to orient on the edge of the tip.