The Tinseth equation is still the best thing we've got, pellets or not. It's pretty darn accurate to my taste buds, assuming about a 10% difference between it and whole hops. So be very careful not to dismiss Tinseth... because there really is NOTHING ELSE BETTER out there anywhere. Just because it all began with whole hops doesn't mean you'll have any idea what the frick you're doing on bittering with pellets if you blindly throw out Tinseth and just use somebody else's wild guesses or your own guesses. Tinseth is still "close enough for most intents & purposes" in my experience, which = "good enough" to meet my own satisfaction.
So I guess what I'm saying is, I'm still using Tinseth, dammit, and I'd encourage all of you to still do the same, until/unless you can provide something better, in which case, I still probably won't believe you.
Cheers all.