Having been to the Claddagh many times now, I can confirm I'm a fan. I've noticed some reviews complaining about the fact it's a chain, but as far as I can see it doesn't pretend to be otherwise. It actually seems to draw more Irish people in than other so-called 'authentic' Irish pubs in Pittsburgh, but I'm likely to think that because I go in to watch the GAA, which always gets 'em in! (It's extremely difficult to find places in Pittsburgh that shows the GAA).
The staff are friendly for the most part (some are great, some are only OK), and the atmosphere is usually good. If you can get a seat at the bar, that's my favourite place to drink. The beer is actually a reasonable price too - I haven't been too shocked by price of anything I've had to drink there.
If you were in the area and in the mood for a drink, you could do a lot worse than this place.