You can find training camp news blurbs to support hyping or hating just about any prospect.
Here's a glowing report about Mendenhall:
http://www.steelersfever.com/forums/showthread.php?t=26219
" The running backs go down to the right end of the field for foot-quickness drills. Believe it or not, Mendenhall has the quickest feet of any of them in the short shuttle where they quick-step through the cones. Mewelde Moore is a close second."
"Willie look okay hitting the hole, but he doesn’t have that extra gear he had in 2005. He better get it back before the start of the season, because Mendenhall is the most pro-ready back I’ve seen at these practices since I started coming here, and I go back to the days of Sydney Thornton. Everyone may assume Willie is the starter, but I don’t think Mendenhall is ready to concede that just yet. If Willie doesn’t get that extra burst back, I wouldn’t be surprised to see Mendenhall start right away. He sees the hole better than Willie, He cuts better than Willie, he has a better lean to the end of his runs (remember that Barry Foster lean that got a couple extra yards at the end of runs?), and he’s a better blocker."
I don't put a ton of stock in what I read in August. It's a long season.