We use Retrospect to backup to encrypted disk images (sized for 25 GB blu-ray) and burn the filled .dmg files to blu-ray disks. At our current run-rate, we're buring about 150-200 of these per year.
We usually get well-priced Ridata bulk media that's sold as 4x or 6x but find that Toast rates them at 8x or 10x. To help ensure reliability, we're conservative with burn rates and normally burn at 4x, sometimes at 6x and have about 2% of the burned media that fails verification. We've often restored from blu-ray media that's many months old and have had no problems. A few times, I've restored from blu-ray media over a year old, also without problems. I've restored from DVD media that's over 5 years old, without issues (we nearly always used DVD-R+ media).
We've always used Pioneer external burners (including when we used to burn CDs then DVDs) in an Otherworld Computing case via FireWire (no, I'm not affiliated with Pioneer nor with OWC but have dealt with OWC for about 15 years). In our experience, the Pioneer burners are natively supported by OS X, are inexpensive and are also quite reliable -- we typically do 300-500 burns before replacing a unit, though we've not yet reached that point with the blu-ray burners. Currently we have 2 Pioneer blu-ray burner models; one BDR-206 and one BDR-208 and the backups are always burned on the newest model.
We use Toast for burning, currently v11 but I think we switched from DVDs to blu-ray with Toast v10. We've used both OS X 10.6 and OS X 10.8 for burning blu-rays (we skipped 10.7). The main system used to do the burns is a 2.66 GHz core 2 duo with 4 GB of memory (running 10.6.8 server) and the BDR-206 is attached to an iMac 3.4 GHz Core i7 with 16 GB of memory (running 10.8.3).
For us, all this works very reliably and we have no problems getting burn rates of 4x and 6x. Hope this helps.