On the contrary to what most people have said, i have been using bio BB's for many years now without problems. I have personally used Excel .25's and the new G&G .25's. Don't expect these bb's to degrade after a couple weeks... it will still take quite a while (still finding bb's outside from several months back) for them to completely degrade. But remember that non biodegradable plastic is oil based and will take tens, if not hundreds of years to completely degrade.
As long as you choose the right brand of biodegradable BB's (mentioned above) they will work just as well a non bio BB with the added bonus of bio environmentally friendlier.