The good news is your bottle isn't going to bounce out with this cage. The bad news is that, despite the marketing saying it's not a hassle to retrieve your bottle, it actually is. Bottles just don't come out easily and have to be worked out, so it's a bit iffy using while riding. I have this on my single speed that I mostly take to work so it's no big deal (can get it out while stopped at a light or whatever), but I wouldn't want to use it on a road bike or if I were trying to remove the bottle while riding.
The cages hold a bottle really well. But I use Camelbak bottles and the cages are really tight unless you use the right bottle. I've found the Camelbak Podium Chill ICE works really well with this cage,since it has a more flexible sidewall and is much easier to pull the bottle from the cage. By the way, the ICE version really does keep your water much cooler. I was out today with a Podium Chill and and Podium ICE bottle, loaded with ice and filled with chilled water. By the end of my ride, the ICE bottle still had some ice in the bottom while the Podium chill bottle was melted and warm. So go with ICE and enjoy with these cages.
I use mostly Camelback bottles because I prefer the spout better than Polar and they are a bit tighter in this cage compared to my last carbon cages. While it is a tight fit, it is not at all difficult to get the bottle in or out of the cage. And my old cages would mark up the bottles with black from the cages due to the bottle vibrating - these don't at all. I think I prefer a tight fit and a clean looking bottle that won't be falling out with a high speed bump.
Really like these cages. Had Tacx Taco cages prior to this which broke after years of service - down side is that they can that they took up a fair amount of real estate. These are much better ion that regards. The do hold the bottles a little snugly - but they are very sturdy cages for what they are made of and are fairly lite.