Cacciatore,
I have had my 45-70 Guide Gun for 3 years. It is ported and I would buy the ported model again. I too had heard/read on the internet, all about how horrendously loud the rifle was and how bad the blast was. I think that all of these "experts" were basing there reports off of the only place they had shot one: at a covered shooting bench at the range. I fired just one round of handloaded 300 gr Hollow point, but my ears did not ring or bleed or anything like that, but of course I was out in the woods.
I have switched to the 400 gr Speer FP bullet now and my load runs about 1840 fps and is very accurate. As far as the other posters comments about shooting cast bullets and the ports shaving lead. I have had no such trouble with my rifle nor has a friend with the same gun. Of course every rifle is a law unto it self. If yours does shave then you have burrs from the porting process and that is easily fixed. Enjoy your Guide Gun if you buy one. Sean