Looks very good. Thank goodness for the digital gauge, I had to do a lot of measuring and test cuts to get a tight fitting miter. Exact matching of opposite side piece lengths is essential, or 45 degree accuracy is moot. Attachment 360403
I finally bought a Grizzly miter trimmer, see pix. and after that all the rough edges of the miter joint disappeared. CAUTION: the griz is wicked sharp and I cut my finger on it when I unpacked it.
The miter trimmer has two wings to hold the pieces, with a stop block on it. However, the wings are really not very well secured and I no longer use them. I match lengths by putting the pieces back to back. Your fingers can detect differences of a couple of thousandths, so this is pretty exact. I cut very precise 45s, usually on my table saw with a Rockler sled. I cut about 1/8th inch long and use the trimmer to slice about 1/16th off each end, with careful length matching on the second piece. When I trial fit, there are rarely any gaps, and the edges are knife edge perfect.
From time to time, I find a bit of a twist or some other irregularity shows up as a mis-fit. If it's not too bad, I use my secret weapon, Tember Mate, which is a wonderful filler that takes stain and finish just like the wood itself. You buy it to match your wood species. It is extremely fine textured and fills even the tiniest gap. It stays put, doesn't shrink and sands smooth. It is an Aussie product available on Amazon. See pix below.
If there is a slight twist or mismatch after glueup, I will sand it down using a shaped sanding block (Rockler), which greatly eases sanding even the most complex shape. I also use 3M Sandblaster Pro, flexible sanding medium, rarely more than 220 grit. The grit lasts forever and takes only a few strokes to produce a baby smooth surface. It also allows rapid evening out of mis-fit joints. I would not use regular sandpaper for this again.
I know what you mean about not wanting to use the good stuff first, which is why I posted this. Fitting mitered corners is equal parts art and craft, and this is how I save the day when there's a glitch.