Dean J in MN
>I've managed to be successful with M&T without a shoulder plane as well. For me, going into the task with "cut it fat and trim" is a recipe for maximizing the amount of time fussing with every joint. So I go at it with, "make it fit off the saw." I screw up from time to time, and when I need to tweak a joint I use a wide chisel. If I need a tiny tweak I turn to a file/float.

As I see it a shoulder plane is set up rather oddly for cross grain work. Typical shoulder planes have bevel up blades (may or may not be low angle cutting geometry), square to the body, and tight mouths. I'd think one would want a boring bevel down, skew blade, and the mouth is non-critical. Sounds like a run of the mill wooden skew rabbet plane is better designed for the task should you want a plane to trim a tenon.

One thing which may separate myself from Bill and others is what I define as an acceptable tenon fit. Most of my m&t joints end up pegged, so the strength comes from tight shoulders and the peg keeping those shoulders tight to the adjoining piece, not from a "perfect" tenon fit.
If I were to rely solely on glue on the tenon cheek to keep the shoulder tight I probably would have to change my criteria. But even then, a chisel is really a fine tool to tune a cheek.

-Dean