Another quick tip which I forgot to mention:
While longpress support (eg the default longpress-enter or longpress-ok to bring up the context menu) is quite handy for remotes with few buttons it adds a small delay - kodi reacts on button-release (as it needs to check if a button was held down for more than half a second) instead of button-press.
If you don't need longpress support for some buttons you can simply override the longpress action with "noop", this removes the longpress mapping and kodi will react faster (as it can now react on button-press instead of release).
eg:
<keymap>
<global>
<keyboard>
<ok mod="longpress">noop</ok>
<enter mod="longpress">noop</enter>
<browser_back mod="longpress">noop</browser_back>
</keyboard>
</global>
</keymap>
See /usr/share/kodi/system/keymaps/keyboard.xml for the default mapping, some buttons have additional longpress mappings for other windows, too (eg in FullscreenVideo).
so long,
Hias