Puchi,

I have seen discussions on sajha on same situation before. Many people who had similar situation like you--currently on OPT, working, and have a valid visa--had travelled out of the US while on OPT and entered without any hassle. However, you need to have an employment letter clearly stating that you are on their payroll or working for them and will continue working for them even after your vacation abroad.

However, this is just an insight; to get more accurate and precise info on this, please consult your college international advisor or an immigration atorney. Hope this helps. Good Luck!