All three and neither at the same time
I have an iPhone/iPad and Mac, I use google daily including their app engine and other services and love my kindle. However, I have problems with all three companies too.
Walled garden and the controlling nature of apple, google's persistence in retaining way too much information for way too long and never truly anonymising it and for Amazon, well it's part them and part the publishers, that old DRM chess-nut.
Were it not for work, I'm not sure I'd own an iphone or ipad though. I'd likely favour a more open device. The Mac however, I don't want to part with
I really like the OS, just wish the hardware wasn't as expensive as it is.
One thing I've been trying really hard to do for several years, is remain platform agnostic. That means I won't buy an ebook unless I can remove the DRM so that should I move from Amazon/kindle to another reader, I can convert the books myself. I try to avoid platform specific apps, favouring cross platform apps (when possible) for my data/docs. Such as using Lyx/Vim/Open Office instead of Pages or MS Office.
The exception is apps for ipad/iphone, where cross platform isn't a choice at all. For that, I just make sure I can get my data out so that it can at least be converted and moved to another platform later. For games, I'm not too fussed. Whilst it'd be nice to buy once and get multiple platforms (as with Steam) it's not really feasible for developers to offer that with the current trend towards walled gardens and 30% splits
Although, I guess "not fussed" is the wrong choice of words, I just won't pay as much for games on locked in devices.
Not quite there yet with all apps though, still a few that tie me to various OS' depending on the task