I think the consensus with most classes is that while some glyphs are so excellent that they're mandatory, there are plenty of glyphs that are so useless, it's almost insulting.
I believe that typically, PVE Priests use the following glyphs:
As seen at MMO-Champion, there are several new and changed (major) Priest Glyphs in 3.1:
Glyph of Psychic Scream — Increases the duration of your Psychic
Scream by 2 sec. and increases its cooldown by 8 sec. (Old: Increases
the duration of your Psychic Scream by 1 sec.)
A PVP-oriented glyph. The PVP gloves lower the cooldown on Psychic Scream by 3 seconds, but with this glyph and with the gloves, you're still looking at 2 seconds longer fear with a 5 second longer cooldown. I don't know if that's worth it.
Glyph of Fear Ward — Reduces cooldown and duration of Fear Ward by 60 sec. (Old: 30 sec.)
I dutifully use the fear ward in a couple of heroics, and I do sometimes wish the cooldown was less than 3 minutes. Even with a cooldown of 2 minutes, I can't imagine anyone needing to glyph this spell.
Glyph of Fade — Reduces the cooldown of your Fade spell by 15 sec.
(Old: Increases the duration and cooldown of your Fade spell by 50%.)
L2Omen. L2Generate aggro. If you need to use Fade so often that you've got to glyph for it, something is wrong.
Glyph of Inner Fire — Increases the armor from your Inner Fire spell
by 50%. (Old: Increases the charges on your Inner Fire spell by 20.)
If someone were to glyph for soloing and/or for leveling, I guess they might look into this one. I guess.
Glyph of Mind Control — Increases the duration of your Mind Control spell by 30 sec. (Old: 12 sec.)
The minute I'm asked to go Mind Control spec, I /gquit. I swear if there are more encounters in Ulduar that involve MC and that make this an appealing glyph for priests, I'll cry.
Glyph of Smite — Reduces the pushback suffered from damaging attacks while casting Smite by 100%. (Old: 50%)
If, as a priest, you are glyphing for damage spells that aren't in the shadow tree, you need to suffer pushback, in my opinion… pushback right to level one where you reroll.
Glyph of Dispersion — Your Dispersion ability now also clears
movement impairing effects and makes you immune to them for its
Apparently the designers who develop glyphs haven't chatted with the designers who develop the shadow priest tree as, in 3.1, the talent already clears movement-impairing effects.
Glyph of Guardian Spirit *new* — If you Guardian Spirit lasts its
entire duration without being triggered, your Guardian Spirit cooldown
is reset to 60 sec.
Much like players who might be compelled to glyph for fade, those who must enhance guardian spirit have bigger problems that a glyph will not solve.
Glyph of Penance *new* — Reduces the cooldown of Penance by 2 sec.
This will bring the cooldown on Penance to 6 seconds. When the patch is released, I will definitely be dropping Glyph of Holy Nova in exchange for this one. Even with all the cooldown timers I have installed, I often find myself reaching for Penance when it's not quite ready to be cast.
Glyph of Mind Sear *new* — Increases the radius of effect on Mind Sear by 5 yards.
Mind Sear currently extends 10 yards around the target. While the increased radius is nice, I don't know that it's so awesome that Shadow Priests will be deviating from the glyphs they already take. Unless, I suppose, they are truly "trash mob" specced.
Glyph of Hymn of Hope *new* — Your Hymn of hope provides 3 times the
normal amount of mana per time, but its duration is 50% shorter.
Much like Dispersion, the glyph and the talent tree departments didn't get the memo. The spell is gone from the game.
Glyph of Pain Suppression *new* — Allows Pain Suppression to be cast while stunned.
This will be nice for PVP Disc Priests, but I cannot imagine anyone taking it for PVE.
If there is reglyphing to be done in 3.1, then, it will be a result of the changes to our talent trees more than these new and altered glyphs. Holy Priests might consider dropping the Renew glyph, for example, now that they'll have a talent to give the spell more oomph.