I have two of these similarly framed revolvers, but the 66 is by far my favorite. I shoot as an amby, so I can nail left or right handed at center mass well over 50 yards with one.
You do have to break them in, HKS speedloaders are pain and the Hogue grips that they sell for them are ridiculously hard to put on - so opt for a Safari speedloader or an SL Variant - plus find some other type of grip rather than a Hogue if you want to install without a gunsmith. (Hogue makes great grips, they just are stupid to put on for the 82, 65, 66 Models of Taurus and the HKS speedloaders work just fine with a 65 or 82)
The action eases up after around 100 shots and you need to shoot it atleast that many times. People that report they shoot better with 38's or 38 Plus P's simply need to keep in mind a .357 Magnum round is just going to be different when you shoot it due to the power, muzzle movement and aim re-acquisition. If you carry that load, shoot that load - it's important. The 66 just shoots different depending on the round, not based on specs of the gun. That said, it's important to also avoid the meme trap of shooting .38's to be cheap, and then load .357 Magnums to carry - that'll get you killed because you want be accustomed to the recoil of the shot in combination with the re-acquisition of POA. Again, shoot what you carry - atleast one or twice, put a few rounds on target with what you are packing or keeping near the bedstand.
I personally favor a Remington 125gr. .357 JHP with this particular model. They are affordable, reliable and consistent rounds to use. The user ahead of me is spot on, the 110gr. or 125gr. JHP white box Winchesters didn't seem to be what this gun wants, however, higher end Winny rounds might be a better flavor of lead.
Like their model 82, be sure you get one past 2008, usually they are good quality. You should work the trigger as often as possible if you bought one new until you can maintain the POA without the 15 pound spring pulling your aim off (too much I might add - if you want it dead on, change the hammer/trigger springs). Once again, I need to stress that dry firing seems to improve the pull if you get one new.
I bought my 66 over a ruger gp101 due to the 7 shot capacity, but may go with that Ruger model later - however, my 66 has not failed, though I was concerned about the tight action (which was more due to the fact I was short stroking the trigger, than it was due to the revolver).
My 66 kept the bears off of me when I was out remote. People who say that .357's won't work on bears never had 180gr. round worth much IMO. If you are loaded 'for bear' - go with Buffalo Bore 180 gr. .357 Magnum or a high end Winchester 180gr. Partition Gold if you can find it (my personal black bear carry) for these fun moments.
As far as defense, if you are looking for a good $350 - 400 revolver, this works fine.
However, it is a heavy piece (keep that in mind), but very much a decent .357 for starters.