I've had no problems with OLCI or printing BPs at all. I've taken at least a half dozen trips this year and it's worked flawlessly each time. You may have some other problem because at least in my experience the system seems to be working fine.

The advantages to checking in online is that the earlier you check in, the less chance you have of being bumped involuntarily. If there aren't enough volunteers on an oversold flight, they will start bumping the last ones to check in. In addition, if you travel with only carry-on baggage, as I frequently do, you can go right to security.