I am using a Samsung GS3 currently with 16GB internal memory and a class 10 exFAT formatted 16GB microSD card. The phone is not perfect, it has a few minor annoyances, but on the whole, it's an awesome device, which does pretty much everything I want it to do. I am running it stock with transitions and all the bloatware disabled...runs smoothly with no lag anywhere. I'd go so far as to say that it's the single best mobile electronic device that
I have ever owned/used in terms of functionality and
ease of use.
I am mostly in areas that have full signal strength or wifi, so I can easily get a full day of moderate/heavy usage (watching videos, full time gmail sync, browsing etc). Battery is around 15-25% at bedtime when it's time to charge. I rarely use the device to make phone calls since I much prefer to SMS or email. I frequently transfer large files (videos and documents mainly) between the phone and my PC, and the ease with which I can do it really makes the device shine for me. Just plug in to the USB port, drag and drop; no need to convert any of the videos...the stock, hardware accelerated video player plays pretty much anything you throw at it, with good battery life too. And there are always excellent free alternatives such as BSPlayer and MXPlayer for those rare pesky mkv files that don't work well with the stock player.
I also carry a microSD-to-SD adapter in my wallet all the time, so for really large files (>4GB), I use it to transfer the file(s) to my exFAT formatted microSD card.
The file explorer options for Android are extremely useful, as are the file compression apps.
I am looking forward to upgrading to the Note 3 or the GS4 (once the bugs have been ironed out) in a few months.