I have no problems of instability. I find it very very light. Instant! I couple with the modulations of the following Simulanalog ... I love it!
I use Boogex ("Mesa Boogie" to me), for two years ... I can not find better for that famous sound! Trash the delicious, Waves GTR and Amplitube are terrible things but not this sound!
This plugin is free! I recommend it to everyone as a result Simulanalog, which also has a very realistic amp!