One of my earliest cycling memories is about water bottle cages specifically. I was about 12 years old and lined up for the Quicksilver mountain bike race, my first competitive cycling event - a loop course of 15 miles or so. Now, such a course might take 90 minutes, but as a child I expected to be out there all day. I had no concept of the importance of weight - my bike was loaded with tools, a full-size pump, seat bag, and most importantly, 4 full water bottles. In addition to the two braze-on bottle mounts on the frame, I had used a "triathlon-style" aerodynamic mount to put two more bottle cages behind the saddle. Apparently I expected to be really thirsty!
Needless to say, it didn't work out. The first time I hit bumpy singletrack at race speed, 3 of my 4 bottles ejected, never to be seen again (this is a great reminder to test your race equipment long before race day!)
The bottle cages in the late 1980's just weren't very good, especially at holding full-size bottles. Bottle cages have come a long way since then and I'm a bit smarter about my bicycle setup as well. With better equipment choices, the ejecting water bottle problem has largely been solved. One of my favorite water bottle cages, especially for bikes ridden off-road, is Silca's Sicuro model, which comes in titanium.
Silca Sicuro Overview
The Sicuro is made by Silca in 3/2.5 (pronounced: "three, two and a half") titanium. Although it's very light at 29 grams, longevity may be even more important than weight. They're handmade in the USA and might outlive you - this is a product you can pass down to your children, or move from bike to bike as your interests and needs change.
If you're riding a road bike, ejecting bottles is much less common, and superlight bottle cages, like Arundel's carbon fiber models, made good sense. But you can't bend carbon like you can with metal, so it isn't a good candidate for tweaking the amount of bottle retention by bending the cage.
With compact frames, bulky front derailleurs, and rear suspension linkages on mountain bikes, water bottle cages or the bottles themselves can sometimes interfere with those frame features, making them difficult, or impossible to mount. Like the similar Wolf Tooth Titanium Morse cage, Silca has adopted a flexible mounting pattern, allowing you to slide the cage up and down to create clearance. A clever solution to this problem. Traditional cages which just have two mounting holes don't have this feature, they can only be placed in one specific spot with no changes possible.
Pros and cons
Silca's Sicuro bottle cages have virtually no downsides, except cost. If you live the "buy once, keep forever" philosophy, these are a fine choice that will probably outlive your bike.