Sorry to be late chiming in on this thread, but it was a busy weekend. Just wanted to take a minute to comment on whether or not there is a "consensus" on how to achieve parallel-ness between miter gage slot and blade. And of, course, with the understanding that such parallel-ness is only one step in the full alignment process. It appears from the discussion so far that there is actually some degree of consensus to be found - we all agree on what is being attempted. We are all trying to get the distance from miter gage slot to a reference surface (blade, plate, sanding disk) the same at any point along the miter gage slot, within acceptable tolerances. Just what those tolerances are depends on the user and the style of work. So far, consensus.
How to go about measuring the distance is where we begin to drift away from consensus. Broadly, I see two camps: there are those who use dial indicators and there are those who do not. The dial indicator folks have provided us with lots of great photos and much interesting discussion. The forum users who are not in the dial indicator camp have been quieter about their methods. I actually have a foot in both camps, so I thought I would describe how I get to parallel. I have used the dial indicator in the past, but these days I use the miter gage and allen wrench method as detailed in PTWFE. PTWFE actually mentions a couple of different methods - first one is dead simple: slide the table up against the reference surface and adjust the table so there is no gap, and the second is little more involved, but not much: use the allen wrench or a 1/4 inch rod and the miter gage to measure the distance. I have found that it is pretty easy to determine if the table is out of parallel this way and if I am interested in quantifying the "out-of-parallelness" it can be done with a simple feeler gauge. I place the allen wrench or the rod from the cross-cut stop block, in the miter gage and extend it so it is snug against a marked tooth or a mark on a sanding disk. But not too snug, as it does not take much pressure to flex the blade or disk. After rotating the blade or disk I move the gage to the same spot/tooth at the other end of the table and note the gap, if any. This gap can be simply measured with a feeler gage if I am so inclined. Last time I checked, I was out about 0.002" according to the feeler gauge. Close enough for me, for sure. Looseness in the miter gage slot does not seem to be an issue. The miter gage bar is adjusted for a close fit in the slot and I keep gentle pressure on the bar against the inside face of the slot.
On a different but related note: another check that I recently started doing was checking the rip fence for plumb. This has always been a routine check on the jointer, but only recently have I started doing it with my saw fences. Surprisingly, the older 500 fences seem to be closer to a dead right angle when locked down then the newer fence. I would be interested in hearing what others have found on this subject.