I recently got a dyson... Eye wateringly expensive, but I hate vacuuming the stairs enough that I saved up for months. I love it so much, it's somewhat embarrassing!
Would it work for you? Well, if you can afford to consider it, then get to somewhere where they're on display and try it. Some people have complained that you have to hold down the button while you use it, which is something to think about with your tendon problems. However, I find that my natural, relaxed grip on the handle is enough to keep it going anyway, as the weight of the unit kind of presses the button into my finger. If anything, it's more of a problem to pick the thing up without switching it on, it's so obviously designed to be ergonomic while running!
Its performance compares very favourably with our Miele, which routinely comes top in Which? rankings. In fact, though the cordless is lower-powered, I'd struggle to choose between them for getting dust and sand up (the Miele is a few years old, though, and I always think that almost any new vac will beat almost any old one, so that might be a factor). As for picking up 'bits', I actually think the cordless is better here. Both are supposed to be for homes with pets, complete with special whizzing brushes, and with a moulting dog, a long-haired human, and lots of thread-snippings, we put them to the test. The Dyson brush has its own motor, whereas the Miele one powers the brush off the air drawn through it. The dyson brush is also much easier to dismantle for disentangling.
Battery power is limited, but then so is my tolerance for vacuuming. I usually run it on standard power, which gives about 20 minutes run time, and then I've had enough! You get a surprising amount done in that time when you're not messing about with power leads, and you're MUCH more likely to get it out to do just one room anyway, so there's less call for long sessions of vacuuming. At full power you only get about 6 minutes out of it, which is a bit of a pain in the arse, but I really don't think you need full power most of the time.