Well, I went to Lee Valley Tools and picked up the Kreg Mitre Gauge Tuesday. Cost $169 CA before taxes. I briefly considered the Incra Mitre 1000SE which was exactly the same price. However the Incra was considerably heavier, it had more hardware behind the fence which would tend to make it more likely to fall off the edge of a table saw and I could see immediately that it had a slightly higher learning curve to properly operate it. Not that the learning curve was a detriment or anything like that, because I'm sure it would have added a little extra capability over the Kreg, but I was looking for simple, easy to use and easy to assemble. The Kreg had that.
Anyway I used the mitre yesterday. What a difference over the stock 6" mitre. With the tape measure properly calibrated, the flip stop properly set, I was able to easily knock off a good 80% of the time needed to cut tenons to an exact length. No more of this sneaking up on a cut line and accidentally going over it with an attendant amount of cursing. I cut in two hours what had previously taken me eight. My buddy who to date has been a little afraid of the tablesaw and never would have considered trying to cut tenons was actually eager to try it out for himself, and he cut them perfectly.
It's nice when you buy a tool that meets expectations. It's really nice when you buy one that easily surpasses those expectations and does the job in one fifth of the time. I should have bought one of these mitres years ago!