I just tried the newest HTPC client and I am confused as to why there is no mouse scrolling and controller support for the most common devices? is that a bug?
Plex HTPC is designed for a remote control (such as my Logitech 650) not keyboard/mouse (although my K400+ does provide some control in Plex HTPC).
Edit- please note there is a bug in the current version that causes some issues with Rew and FF functions via MCE remote and also for some users, Play/Pause.
Depending on your setup. Using modified input mapping does not currently function but has been fixed for the next version. Reverting to an earlier version works in the meantime.
I am using Flirc so can assign buttons as required.