I changed to BP/W based solely on the research (mainly on SB) as well. No regrets there.
First time in the pool with a BP/W, most noticeable changes were
1. More free around the torso, there is no hugging feeling as with a jacket BCD
2. Trim definitely feels more natural
3. Much more easier to utilise D rings, as the rental jacket BCDs I've used before always had D rings in weird places that either dangle when clipped, cannot be found easily, or is just plain impossible to clip off without contorting yourself.
4. No feeling of the BCD riding up, due to the crotch strap on the BP/W
However, as much as I love the BP/W, there are definitely some changes that you have to get used to before feeling comfortable with it.
1. Setting up is a more complicated process compared to the jacket BCD, but once you get it correct, it will feel loads better than a jacket BCD. Just experiment around with different configurations, tweaking the height of the wing on the backplate, the length of the straps, the position of the D rings etc until you find a configuration that you like.
2. No pockets that are usually available with jacket BCDs. I used a thigh pocket and also changed to the longhose configuration in order to take full advantage of the tried and true Hogarthian configuration.
3. As you would likely be spending much more time in trim now, you might have to get used to doing skills in trim (such as regulator recovery, mask clearing, dumping air, shooting a DSMB etc) rather than in the upright position as is common with jacket BCDs.
4. You might need some time to get accustomed to the rear dump, as BP/Ws usually have rear dumps that face inside (facing the diver), rather than outside (facing the surface).
5. Learn how to don and doff a BP/W harness (involves pulling the D ring on each of the shoulder straps). It will be a piece of cake once you get the skill down.
6. Experiment with weights and again, as the amount and distribution of weights will definitely have changed. Also consider whether a weight belt will interfere with the waist strap of your harness.
7. Had no issues with staying upright on the surface, but read that some divers had to experiment around on their weight distribution to being faceplanted into the water on the surface.
TL: DR, changing to a BP/W before trying it out shouldn't be too much of an issue, but would recommend you to factor in some time to get comfortable with the BP/W, and not just push your limits on the first dive, or leave the first dive with the BP/W until the the day of your expensive dive trip.