I think I must not be experienced enough to have really developed ingrained habits. I just got back from 4 days of diving down in NC with my new 45 degree Nauticam VF. I was shooting at WA and CFWA.
I thought the VF was great, right from the first dive. Not to say that I had zero issues. Issues that I encountered were:
Objects in viewfinder are closer than they appear! One time, I was tracking a shark in the VF and swimming slowly, to get it lined up how I wanted. I was looking at it over the gunwale of a wreck. I could see the gunwale in the VF, but I didn't realize how close I was to it until my dome actually ran into it. Fortunately, not hard and no damage. Another time, I was tracking a smaller shark that was inside the wreck, between me and a wall. I was snapping as it came closer, but when it finally started to go past and I looked up from the VF, I realized that I had trapped it between my camera and the wall. It's pectoral fins were hitting the wall and my dome to wriggle through.
It is harder to see stuff. For example, I was composing a scene in a hold of a wreck where there was a shark and a bait ball in the far side of the hold. My composition was to take in almost the whole room, but the focus was to be the shark and I was waiting for that moment when the bait ball coalesced momentarily around the shark. Looking through the VF, I could not see the shark well enough to tell when the right moment was happening. I had to look up, not through the VF to really see what the shark was doing.
Swimming and watching a subject in the VF was also more of a challenge to my buoyancy. I found myself watching stuff in the VF to use as a reference for whether I was starting to go up or down. But, when you're looking down at a 45 to see something that is straight in front of you, then sort of taking in the peripheral view (through the VF) to have an idea of up/down movement was a little disorienting.
But, none of that outweighed the benefits that I enjoyed. The biggest one, for me, was that I was able to adjust the VF diopter so that I could easily read my camera "screen". I normally wear reading glasses, but I don't have prescription lenses in my masks. So, reading my camera settings on the back of the LCD has always been somewhat of a squinty affair and not 100% reliable. Previewing photos on the LCD was never sufficient for me to tell if things were in focus. Only that the color and basic composition was right. Looking through the VF, I could easily read the camera settings on the screen and see previews very well.
Also, I am often trying to shoot at somewhat of an up angle and the VF was REALLY nice for that.
And that was all only with 3 days of actual shooting. I am looking forward to getting even more comfortable and quick with it.