The main problems I've had with Samsung devices have been due to the fact that Samsung so heavily customizes Android, it's virtually impossible for them to deliver Android updates on any kind of reasonable schedule.

At least now, Samsung delivers updates. At one point, not so long ago, any non-flagship Samsung device was stuck on the version of Android that it shipped with, unless you were willing to root it and install your own ROM.

Then, there's the fact that Samsung insists on shipping its own e-mail, messaging and contact management applications, which are very difficult to back up. There's nothing quite like having to tell someone who bought a new phone that they have to type out all of their contacts by hand, because they used Samsung's contacts app instead of Google's.