In my opinion, those who say "Hash patches are great for organic modeling but are lousy for mechanical modeling" aren't complaining about what you can model with A:M. They're complaining about all the missing tools on which they've become dependent when using polygon based modelers. And the reason they're dependent on them is because there is no other way to realistically wrangle polygons. Although automatic filleters, lofters and booleans would make modeling in A:M easier and faster, they wouldn't necessarily improve the quality of the models.
Keep in mind that A:M's toolset is designed for character modeling and especially character animation. This implies to me that Hash patches are optimized to build and animate heads, faces, arms, legs, fingers etc. Compared to most hardware these are small, highly curved, textured surfaces moving in organic ways. So if you're modeling the hood of a car with smoothly flowing curves, don't fall into the trap of thinking that you can only use a few control points (cps) to define the general shape and then tweak magnitude and bias values to get the final shape. This may produce an acceptable surface, it may not. It depends on the surface and the desired level of detail. Personally I would like to use as few patches as possible but still have the model's surface quality stand up to an arm's length inspection.
If you ask me for the secret to good mechanical modeling in A:M; it's having the desire to sweat all the details because the program's not going to do it for you. Fileting edges and smoothing surfaces in A:M can feel like a long, tough slog if you are used to a polygon based modeler. Using A:M's modeling tools, you cannot take a 50 mm cube primitive, automatically apply a 5mm bevel to its edges, automatically bore a 10 mm hole through it and then fillet the holes' edges. You have to figure out (first through trial and error, eventually through experience) the correct spline configuration that defines a bevelled cube with a filleted hole in it. (A:M's implementation of Boolean cutters is a rendering trick, it does not re-arrange splines). Compared to polygon tools, modeling hardware in A:M can feel like using a pair of pliers to drive nails. It works well enough but it's not really the optimal tool. But those pliers are so danged cheap compared to the over-priced hammers that other 3D software companies sell.
As someone who has modeled nothing but hardware, I have written these tutorials in hopes that they will be useful to other A:M hardware modelers. (With A:M's emphasis on character animation, we need all the support we can get). I assume that you are already familiar with A:M's tools and terminolgy. If not, a good place to start would be Basic Splinemanship, Part 1. The last link on this page leads to images of hardware that I've modelled in A:M so you can judge if my advice is worthwhile.
Not surprisingly, most of the following pages are heavily illustrated. They are best viewed at a screen resolution of 1024 x 768.
Modeling Mechanical Surfaces - Random Questions & Answers
Adding Bones to a Vehicle
Modeling Bump Decals
Adding Rivets: CP's or Decals?
Modeling Edges and Corners
Modeling a Concrete Block Wall
Examples of my Modeling