beside kontakt and dfx buffer override reaktor session is the only vsti(win xp)/audiounit(osx) that is used in nearly all of my tracks. i can't complain about many crashs, although i had some, but mostly i can avoid the situations that lead to the crash(e.g. cpu overload). the included library is very good, but the main reason i bought reaktor session was the user library that can be found on the website of native instruments. i know no other collection of plugins(or something like that) beside pluggo that offers such great tools for sound manipulation(fx). but also the ("virtual analogue") synths sound very good(of course i tested not every single reaktor ensemble). the gui depends on the used ensemble(there are some that are very hard to use), but in generally the main features(and most of the ensembles) are very easy to use. the support at native instruments is good i think(i only mailed them once, but there's also the forum on ther website). with only a sequencer and reaktor session you are very well equipped for every kind of (electronic) music.