Nexus 5 Android Marshmallow Problems
The Android Marshmallow Developer Preview process has helped Google and its developers weed out potential problems with Android 6.0. That said, we do expect Android Marshmallow problems to slip through the cracks.
Large updates like Android 6.0 Marshmallow always come with their own collection of problems. There will almost certainly be some initial bugs and we expect Nexus 5 owners to run into performance problems that include battery drain, poor connectivity and more. These are common after major updates.
We don't expect these problems to affect every single Nexus 5 user but you'll still want to prepare and you'll still want to have a list of potential bug fixes handy just in case something goes wrong with your phone.
If you start feeling leery ahead of the Nexus 5 Android 6.0 release, you should hold out for a few days and gather feedback from us and other sources.