if you are referring to the Arduino 1.0 IDE, then yes, all the shields that were compatible then are compatible now, in terms of hardware. if the libraries for interfacing the Arduino to the MP3 shield are not updated to 1.0, it can be done very easily yourself.
the latest Arduino code is here: Google Code Archive - Long-term storage for Google Code Project Hosting.
i opened the example in Arduino 1.0, and yes the code doesnt work right off the bat, but no big issues that are hard to fix