The two salts I regularly leave out of the boil are Chalk and Baking Soda. They are typically only good for raising RA for the mash pH. Also, if you need to use Gypsum and others to drastically lower RA, you'll likely get all the SO4 you'd need out of the mash addition so you wouldn't want to layer more on top for the boil.
Ok, I see now. I also don't see why I'd ever add chalk to the boil. Good point. I see now why you're given the option of splitting mash from boil. Makes sense to me!
Hey Kal, I just noticed your little notes below your sulfate about 50-150 being normally bitter and up to 350 being really bitter. How's that range working for you?
I forget if I have read about that in Palmer or not.
I frankly can't remember where I read it either... I think it was in Palmer's book. (edit: oops - you guys already mentioned it!). I just cut and pasted it in there to give me some idea of what to aim for...
I probably have a few other notes here and there I added based on information that I thought would be useful to me.
How well does it work? Good question! I don't know!

I've done water treatment for my last 5 batches brewed over the last ~4 weeks or so but none of the kegs have been tapped yet!
I made 11 gallons of Munich Helles today (4.5 SRM) using basically my second set of numbers from above:
Starting Water (ppm):
Ca: 8.9
Mg: 2.2
Na: 16
Cl: 6.1
SO4: 27
CaCO3: 32
Mash / Sparge Vol (gal): 7.3 / 9.4
Dilution Rate: 0%
Adjustments (grams) Mash / Boil Kettle:
CaCO3: 0 / 0
CaSO4: 1 / 1.3
CaCl2: 5 / 6.4
MgSO4: 3 / 3.9
NaHCO3: 0 / 0
NaCl: 0 / 0
HCL Acid: 0 / 0
Lactic Acid: 0 / 0
Mash Water / Total water (ppm):
Ca: 66 / 66
Mg: 12 / 12
Na: 16 / 16
Cl: 93 / 93
SO4: 90 / 90
CaCO3: 32 / 32
RA (mash only): -23 (3 to 8 SRM)
Cl to SO4 (total water): 1.04 (Balanced)
We'll see how it turns out....
Funny enough, I've done 5 batches now from 4-15 SRM and while the RA numbers I come up with should lower my mash pH far enough to get reasonably close to 5.2, for the last two really light beers (last one was a Helles at 4 SRM) I had to end up using a little bit of lactic acid in the mash. In the case of the Helles today noted above, I used 3ml of 88% Lactic Acid in 7.3 gallons of mash to get the pH down from 5.66 to 5.33.
It would seem that (at least for me) if the spreadsheet gives an SRM range then I need to target the upper end of the range (ex: the numbers above say it's good for a 3-8 SRM beer but for me I'll only get pH into range for the higher end, or 8 SRM). For very light coloured beers it's meant using lactic acid a bit. The darker beers (10-15 SRM) that I made previously seem to get a mash pH to low enough (5.3-5.4) that I don't bother. Having a pH meter is a must!
Kal