The premise is simple: I'll tell you what players you can confidently start the season with, and what players should cause your stomach to wobble if you have to start them.
2006 stats at NFL.com and pro-football-reference.com
Willie Parker (RB): Honestly, when I looked at the 2006 numbers at the end of the season, I was surprised to see Willie Parker among the most productive fantasy RBs in the league (in my league, he was one of three good RBs on a last place team, believe it or not, so I didn't pay terribly close attention to him). But he was, and he will likely be a top-10 pick in 2007 fantasy drafts.
Hines Ward (WR): even after a mediocre 2006 season, he's still a worthy starter. If he's your #2 WR, you should be confident: you can depend on solid numbers, and he could put up great numbers.
Jeff Reed (K): The Steeler kicker has consistently been a solid fantasy scorer for years.
Defense: Under Bill Cowher, the Pittsburgh defense was always a great fantasy unit, getting sacks, turnovers, and touchdowns. I don't expect a lot to change with Mike Tomlin as the coach.
There are other Steelers you should think about drafting, but not as week one starters.
Ben Roethlisberger (QB): a good QB, but you should be able to find 12-16 better fantasy starters at the beginning of the season. He's a good fantasy backup that you could feel good starting a few weeks a season if forced.
Heath Miller (TE): He hasn't piled up yards yet, but he's a talented TE that does get touchdowns.
Santonio Holmes (WR): As a rookie he had 824 yards, so there's definite potential that he could be a fantasy starter midway through the season, or earlier.
There's another advantage to drafting Steelers for your fantasy team: they're on TV all the damn time, so you'll get plenty of chances to watch your players.