My first brew was a SN Porter clone, extract w/ specialty grains. We taste-tested alongside the real thing and it was close, only BETTER. I had several friends over to try it and they all agreed the homebrew was better. Unfortunately we didn't do a double-blind test or anything. The homebrew just tasted richer, and more flavorful. This is coming from a guy whose favorite porter was Sierra Nevada (before I started homebrewing, that is).
Here's the recipe:
8 lbs Light LME
.5 lb Chocolate malt
.75 lb Crystal 60L
1.5 oz E.K. Goldings (whole leaf) (60)
.75 oz Willamette (whole leaf) (10)
WLP001 Cali ale yeast, no starter.
I tried modifying this recipe by adding another lb of LME and some black patent malt for a darker color, I wasn't impressed, I liked the original better. I'd consider brewing it again with the black patent as it shouldn't affect the flavor at all, but with the extra lb of LME it was too malty and too boozy (6.31% vs 5.67%) I also did a late extract addition the second time I brewed it and so I'm sure that changed the IBUs a bit. I would either do the whole extract addition at the beginning or scale down the hops to target 28 IBUs (use 1.2 oz Goldings instead if you do a 50/50 late addition).