Hello. Current Mk III trigger pulls are heavy but many are crisp. Depending upon the magazine disconnect in the individual gun, they may or may not have a "gritty" feel to them. This can be fixed if you like the gun.
Since the Mk II, Hi Powers tend to feed about any JHP one cares to feed them.
This was not always the case and I think a number of the lingering complaints about some HP's being "finicky eaters" comes from the older guns which had the humped feed ramp. Every Mk III I own, have owned, or shot worked fine with every JHP I tried...and that was a great deal of what's available.
If you opt to get the Hi Power Mk III you may wind up with one having a decent pull out of the box. A friend recently purchased a couple that did. If not, and you like the gun well enough to want trigger work done, a very nice and clean 4 1/2 pound pull is well within the capabilities of HP 'smiths.
Best and good luck.