To date, I've re-barreled only one short & one long Howa 1500 - the SA was barreled with a Bartlein 1-7.8tw, .237" bore in 6XC; put a 26" Krieger #5 sptr 1-9tw in 280 AI on the LA. Dialed both actions in on a GreTan-style action truing fixture, and neither one had more than .001" runout on the face, lug seats were also within .001", and when I picked up the threads and re-cut them, they were so nearly concentric that I certainly felt like I'd wasted the time it took to dial it in in the first place. Like I said, I haven't done a whole bunch of the Howas, but the ones I have done didn't need anything beyond a good chamber in a good bbl, a 20 MOA scope rail, and perhaps a lighter trigger.
The action I've got in the shop right now is another SA, but is one with the new HACT trigger; this one breaks at 2lbs, and is pretty crisp. Will probably shoot it as-is with this trigger for awhile before making the decision whether to put a Timney on it or not.