I do, regularly. I read books on my phone on the go, then pick it up at a computer (and I do this across multiple computers) when I'm at a computer, and vice-versa.
Take BookFusion for a spin and let me know what you think. BookFusion allows you to easily read your entire eBook collection and sync your bookmarks, reading progress, highlights and comments across all devices. BookFusion has native Android, iOS and Web apps.
It syncs all elements of all of my activities across all platforms (Windows, OS X, Android, iOS) that I use. My main issue with it is that I can't download the stuff I uploaded, so it's not really good as a storage/backup solution, but that's fairly minor.
Would be interesting to hear your feedback if you decide to try BookFusion
Does BookFusion let me re-download books I've uploaded?