Count me as one who loves the Ruger Bisley.
The advantage to the freespin pawl is two-fold. Mainly, it corrects the issue with unmodified New Models in that when loading and unloading, if you go past the click, you have gone too far. You must hold the cylinder against slight spring pressure to keep the chamber inline with the loading port. Not a big deal if you're taking your time but this is the definition of frustration when trying to run one fast. The second advantage is that you can spin the cylinder in both directions so that if you have a bullet jump crimp, you are better prepared to remove the offending cartridge.
There are no disadvantages. I have had this done to three of my guns and it works wonderfully. However, I would still rather have a half cock notch but that's a much more expensive option, $30 vs $200.
The "reverse indexing pawl" of the New Vaquero and all the late model flat-tops is also a wonderful addition. It is essentially a freespin pawl with a spring loaded plunger added to engage the ratchet teeth on the cylinder to correctly align the chambers for loading.