Sure, I've done it plenty on both VMWare and MSVS. Performance issues were directly related to how much resources I gave (or took away) to the virtuals and how many virtuals were running on the host. Remember your virtuals probably aren't as powerful as your stand alone workstation.
Just FYI, in your Robot code make sure you put in wise wait cases. Don't just put in delays but put in waits for certain things to happen or appear before moving to each next step. This way you can be more assured that running a Robot script on a slower box will still complete the same way it does on a faster box.
If this or any response has helped you, please reply to the thread stating that it worked so other people with a similar issue will know how you fixed your issue!