Can anyone recommend a good VLC alternative?

smplayer (based on mplayer) plays all formats known to mankind and is easy to use. It also has unique features such as remembering the position in a movie when you close it.

GNOME Media Player

GNOME media player is a fairly simple media player that fits well into the GNOME desktop.

It runs on multiple backends (vlc, gstreamer and xine) which means it can play almost every media format. By default it tries to pick the backend that works best for what you are playing. It doesn't have as many features as some other players but it has a simple interface and from my experience plays well.

If you are fine with Movie Player/Totem (Ubuntu's default media player) or Banshee, you can simply install the codec packages (and their dependencies) to play all the formats:

sudo apt-get install gstreamer0.10-ffmpeg gstreamer0.10-fluendo-mp3 gstreamer0.10-pitfdll gstreamer0.10-plugins-bad gstreamer0.10-plugins-bad-multiverse gstreamer0.10-plugins-ugly gstreamer0.10-plugins-ugly-multiverse

PS I use this instead of the ubuntu-restricted-extras because I want only the codec packages. The restricted meta-package contains some fonts, OpenJDK and codecs.

EDIT I checked just now, ASS/SSA issue I mentioned before is no longer applicable.