I've made a similar switch, going from an Avid to a Zeagle Tech. I found a few differences that took some getting used to:
1. The back inflate of the Ranger/Tech changes your buoyancy characteristics on the surface considerably. With the Avid, I found that the more air I added to the BCD, the more stable and comfortable I'd be, and it'd keep me in an upright position. The back inflate BCDs tend to tip me forward, particularly if I've got a lot of air in it. I learned to compensate by adjusting my body position in the water, tending to lean back more than I used to.
2. With the Avid, I used to be able to sense how much air was in the BCD by how it felt against my body because of its jacket-style design. When I went to the Tech, I didn't have that feedback anymore. Not a big deal, just a bit of an adjustment.
3. The Zeagle power inflator isn't as responsive as the Avid inflator. I had to get used to holding down the inflator button longer on the Tech than it took to get the same response on the Avid. The Zeagle is also trickier to purge than the Avid because of its long deflator hose - I have to take more care that I hold it up when venting so it doesn't trap air.
All of these things take a little while to shake down, but I'd figured it out within my first dive and was really comfortable with it within 5 dives. On the plus side, the Zeagle is much more comfortable, has a better weight integration system, and I found that the releases were easier to use with my drysuit.