I switched to Vacu-grips a few weeks ago. I was able to get used to them after about five frames, and I shot my first 800 series just one week later. Love, love, love the Vacu-grips.
I used to have trouble with my hand swelling a lot, but I reduced that with a little shorter span, a little less reverse in the thumb to lock my hand in more securely, 1/8" reverse in my fingers, and Vise Hada patch on the back of my thumb to reduce friction and drag on my thumb. It's nowhere near as bad as it used to be, I was able to bowl 21 games in a tournament awhile back with zero swelling problems.