That's quite an offer.
EugeneStyles gets right to the bottom line: if you don't believe Pedro has a good chance of making it through the season without spending extensive time on the DL (translation: if you'll be pulling out your hair all winter if you accept the deal and he becomes injured), close the door on this and don't look back. Trust me.
If, on the other hand, you believe Pedro's fine and usually have a stoic or zen mindset when the risks you take don't work out... well, you've still got a very tough decision. I think it'sbeenawhile hit the nail on the head here: your rotation needs an ace - at the moment, you need too many breaks to go your way. If you're playing roto, I agree that you need to ensure that you get a second closer (through this trade or from another source) before you can accept this deal. If it's h2h, this probably isn't as pressing.
If this were my team, I'd accept the deal, but that decision is based more on style of play than objective reasoning. I tend to go after high-risk/high-reward players; sometimes it works, sometimes the results are catastrophic.
Still, this call is so tight that going by playing style (or instict, or whatever) may be the best way to go here. Since we can see neither into the future nor into the workings of Pedro's arm, the only objective ways to call this seem to be:
a) Where are you in the standings? If you're in the money now, or very close, I'd stay. If you're trailing, hitch your wagon to Pedro and hope he pulls you to the top. Piazza is the very best at the weakest position; Pedro can dominate a league.
b) The sp's due for call-ups relatively soon look pretty solid; there might be a gem or two among them. Impact catchers are another story: there won't be many chances to pick up an upgrade over Lieberthal, much less a Piazza-caliber stud.
Anyway, when all is said and done, I'd want Pedro as my ace and throw caution to the proverbial wind.
Hopefully, a few more opinions will be forthcoming here. I don't know if they'll make the decision any easier, though...
Ausmus and Prior?