Even if physically Arduino shield compatible, watch out for 3.3 vdc Vs 5.0 vdc shields as damage can be caused if mismatched. The latest shield pin out (rev 3) has a 'new' pin which outputs 3.3 or 5.0 to 'tell' connected shields if the underlying controller board is working at 3.3 Vs 5.0, so the shield could theoretically switch voltage level converters to allow proper operation, however I've never seen such a shield product available?