I have used the Sidewinder x5 and will vouch for its performance, however I did find Mouse 4 and Mouse 5 buttons were uncomfortable to use (they are small and circular). I currently use a G9x and find that much better. as for the G400, I would recommend the G500, or the - Thermaltake Tt Mouse over it. I found those two much more comfortable to use. yet it is more personal preference when choosing a mouse...that and somewhat how you hold it.