1) PF fish seems to be getting better reviews for their D2 over other makers. Is it even worth the K110 uncharge (say, on the Flavorist)?
I'm not sure. I haven't used it and I have not seen it reliably tested. The theory is that K110 is basically German D2 but is made to stricter quality controls than the usual Chinese D2. So in other words, it feels like an answer to one of the two potential issues I raised regarding Chinese D2. While I wouldn't expect the heat treatment to compare with customs or American knives costing three times as much or more, it at least seems to make sense as a modestly priced upgrade for companies who mostly work with Chinese D2.
2) Price aside, what do you think of the Flavorist vs 818? Reports are their Micarta isn't the best, and it's a front flip, but what do you think?...
I haven't tried the Flavorist. It's obviously a different design. Dovetailing with some of the other benefits you gave for this price range, there is a fairly low barrier of entry to just trying it out.
... no aversion to Micarta. Just saw that it's more variable from maker to maker than G10.
While G10 is fiberglass set in resin, Micarta is a diverse class of materials involving fabrics set in resin. Micarta can be finished in different ways to achieve different effects, from smooth polishes to fuzzy bead blasts. Honestly, that's all part of the fun with Micarta. What you like will depend on you.
The only Micarta I have handy from Petrified Fish is their "Flax Micarta". While nothing to write home about, I definitely prefer it to G10. One of the things I really like about the Sencut Neches is the particular finish they do on that Micarta. It is a good example of a slightly fuzzy finish that feels soft to the touch while still being resistant to the elements.
3) Rough scales: do you file the edges?
It's more an issue of coming to crisp edges than overall roughness. For instance, the line created by a hard 90-degree transition can be uncomfortable to some people. I tend to round those over via sanding. Coincidentally, I've found that my wife's two-sided emery boards are perfect for most average G10 and Micarta (polished finishes require finer grits). Just start with the coarse side and finish with the fine side.
(Note that the dust created by sanding is bad for your lungs. While hand-sanding small areas on scales doesn't generate a ton of dust, definitely do it outside or take other precautions to avoid breathing it into your lungs.)
Bonus question: Price aside (I realize this is a "value" thread, but I'm curious), what do you think of Kizer? Specifically the Kizer Cozy?
I'm a big fan of Kizer. If you follow the EDC picture thread, you'll see their knives in my pocket on a regular basis; including several examples of modified scales.
The Cozy is a cool knife but the handle contour just did not fit my hand very well.