Let me preface this with I got back into serious fantasy gaming with the advent of FrostGrave. While I was waiting for my Kickstarter to arrive, I wanted to build up a couple of warbands, but I didn't want to invest a huge amount of money. I went down to my FLGS and found a box of FireForge Teutonic knights on sale for about 12 dollars, so I snatched that up to build my soldiers. I turned around and saw a huge rack full of Reaper Bones miniatures. The stark white miniatures threw me for a loop, but the price was right so I grabbed about four different minis for various soldiers and wizards.
Let's just say that the first lesson I learned about the Bones miniatures is that spray primer or any primer is unnecessary. As a matter of fact, the spray primer that I have always used had an absolutely horrible effect getting both tacky and fuzzy. It was so bad that I set the minis to the side to revisit on another day. From that point forward, I only use Gesso or airbrush primer, and only if the figure is intended to be primarily dark or metallic. Anything else, I just paint directly onto the figure.
Some of the figures I've picked up were distorted, but having been an old hand with resin, I already knew about the hot/cold water tricks. One thing I've noticed is that the thicker the piece, the longer it needs to soak and the water needs to be hotter. I tend to get water to boiling level and let the piece soak as needed. When I was repositioning my Hydra, it took boiling water and about a 5 minute soak to get the necks flexible enough to reposition. The legs took almost no time in comparison. The ice water bath locked it in place.
I've noticed that the larger figures seem to be better at holding their details in the white Bonesium material. I'm hoping the new darker Bonesium will prove to be better at holding details for all of the figures. I picked up a 77058: Almaran the Gold, Paladin. The facial details were non-existant. I cut off the head and replaced it with a FireForge helmet.
Conversions: I have to say, the Bonesium makes conversions a breeze. I picked up the Kobold set which comes with 2 each of three models. I was able to swap arms or hands on 4 of them so I would only have two duplicates. The Bonesium material cuts easy and superglue sets it almost instantly.
These have been my observations and as with anything else, your mileage may vary. I don't think I would want to replace all of the figures with Bonesium, but if you're looking to save some money or bulk up on your critter collection, Bones is definitely the way to go.