Absolutely OK to buy a refurbished MacBook Pro - but ONLY buy it directly from Apple. You have a return privilege in case you are not happy, and it comes with a Warranty. You can also purchase Apple Care (the only electronic I always purchase an extended warranty on).
I work in this business as a developer (not an Apple employee, but develop software for iOS devices). I most recently bough the MacBook pro Retina 13" and was able to get a refurb form Apple for about a $500 savings. I update my hardware every two years and my recommendation would be to only look for a current version as a refurb (not an older model as you may find both), and depending on the day and time you may have a variety of processor and hard drive options to choose from.
Although Apple states that there may be visual defects and such in the device (e.g. nicks or scratches), I have never seen this, and you wouldn't know that it wasn't brand new from the store except for the plain white box that it ships in. They also give it a new serial number which identifies it as a refurb in their system, but that's about it.
Quite often, people buy these new, return them in less than 30 days for whatever reason, and Apple can no longer sell that device as new. Some can be repaired for manufacturing defects, but are in complete working order once they arrive to you. Don't be afraid on this one - so long as you buy directly from Apple. Good luck!