[otrs] OTRS and ITSM versions

Dear All, Can somebody please give us a pointer regarding the evaluation of OTRS? We are planning to evaluate OTRS with the ITSM modules. I heard that OTRS version 3.0 is not yet compatible with ITSM or vice-versa. Is it correct? If this is correct, should we evaluate the older version of OTRS which is 2.4 and much stable. Which ITSM version we should evaluate with OTRS 2.4? We are looking for ITIL processes along with basic OTRS functionality, so appreciate if somebody show me a direction please. Regards Sudhir