Doc Halladay: Worth it?

The trade deadline is approaching, and this year the big name is Roy Halladay. Granted he is probably the best pitcher in the MLB right now ('08-09: 30-14, 369 IP, 2.80 ERA, 1.08 WHIP), would he hurt a team's farm system too much for it to be worth it?
He is signed through this season, and he would have the option to opt out next season if he is traded. You would think he is going to demand top dollar, maybe more than CC and Johan are making. So not only would the trade demand top prospects, if you want to keep him after this year, it will cost top dollar (Blue Jays GM also said that he will not allow a window to negotiate a contract, unlike the Johan Santana deal).
So the question is, for a team like the Phillies, Yankees, Cardinals (who are all reported interested), would it be worth it? The Yankees are said to have to give up Hughes and/or Joba on top of 2 top prospects (Jackson and Romine, most likely). While it may cost more for the Yankees since its an in division trade, Riccardi (Blue Jays GM) has said that he does not mind trading within the division, he just wants the best deal possible.
So back to the original question. Worth it? Is it worth giving up 1 or possibly 2 young players that have already played in the majors, on top of a few top prospects, as well as taking on a lot of money in the process? YES. It is worth it. Why? Because for a team like the Yankees, adding Halladay will not only guarantee a playoff spot, in my opinion, it will make their rotation for the playoffs unbeilevable. Doc-CC-AJ-Pettite. For the Phillies, Doc and Hamels seem like a 1-2 match made in heaven.
No matter the deal, as long as you aren't hurting your MAJOR LEAGUE team right now, it is worth risking some of your future pieces to get argueably the best pitcher in the game.