Bicycling on steell pavement could be very slippery expecially when its raining.
Seriously though, one of the best things you can do is get something like google maps and check out possible routes. What I did and still is doing when necessary, is I would then drive around the said routes and observe posible problems/concerns. But the real test is riding the route yourself. Don't get discouraged by what you hear. Most of the time its from people who are just coming up with excuses not to ride. You should go and find out for yourself.
Lived in the 'Burgh for about 10 years. Try going to Pittsburgh Pro Bikes in Squirrel Hill. Ask for Al...he's up on all the latest in town and knows everybody remotely connected with cycling. Great guy, I learned alot from him. While I didn't commute per se I rode quite a bit and can say for sure to NEVER ride on Routes 28 or 65. There's several bike messengers who live on the Southside. They know all the best routes and bike trails. See if you can get hooked up w/t guys(and gals) who do Urban Assault(nightriding...you'll need good lights, full suspension, helmet, nerves of steel and the cunning of a burglar).
Danny Chew lives there(former winner of the Race Across America). He started and continues to spearhead the Dirty Dozen ride. 13 killer hills within 5 miles of downtown on a 50 mile ride the Saturday after Thanksgiving. No money, no medals, no mercy. I did the course a few times training for a lengthy tour and can attest it's not for the recreational cyclist.
Pittsburgh is a great cycling town once you learn it. But, you're right it's not for the fainthearted.