Groupwise 2012 platform choices

I'm planning our upgrade to Groupwise 2012 and want to move our POA and MTA to a new server. We are currently running on OES2 and want to move to either SLES11 or W2008R2. I'm looking for feedback on the performance and reliability of running GW on Windows servers. Are there any performance tuning best practices for W2008 for GW? Are there any definite pitfalls? I have not been able to find anything substantial in my searches other than a difference in disk performance (which may be more environment related). Our Post Office consists of about 300 users, a total of about 400 mailboxes, and disk usage of about 65GB.

I appreciate any info and experiences anyone can provide.

Thanks.