I agree with everyone rioting about Nitro Charge. Fire Blast/Earth Power/Dragon Pulse/Explosion was an insanely common moveset last gen, someone explain to me how replacing Explosion with Nitro Charge is a step backwards or even a lateral move. There wasn't that much less fighting type priority last gen than there is now.
(Edit: by the logic being used by those opposed to Nitro Charge sets, no pokemon weak to priority should ever use a speed boosting move. wat.)
Heatran is not a frail mon. A Nitro Charge set would all but completely outclass the ubiquitous (at least in 4th gen) Scarftran, IMO. You can switch moves, do damage while boosting, boost beyond +1, and have a free item slot, and all at the pathetic cost of a turn (not a big deal, Heatran can take a hit, and its not like a Choiced Heatran or choiced anything for that matter wouldn't lose you plenty of turns switching), and a moveslot, which was previously taken by Explosion which is now crap. A coverage move? What are you going to cover that Fire/Ground/Dragon doesn't? Burunkeru with Dark Pulse? No.
As far as its commonality on sets on PO or whatever... the metagame is still in its infancy. Who the fuck used Tormentran, the Specially Defensive set, or hell, half the sets on
http://www.smogon.com/dp/pokemon/heatran in the first few months of the 4th gen?
tl;dr the point of comparing a Nitro set to Scarftran is to show that a set that completely outclasses the most popular set from 4th gen is worth a mention at the bare minimum in a 5th gen analysis.