The GUI looks really nice and compact. All the features are right upfront or on the back panel. Everything is one or two mouse clicks away.The looks give you that futuristic drum machine look. The Sound is very crisp and clear. I tried the sample kits from the RMIII inside the RMIV and they sounded more distinctive and brighter in the RMIV. The synth modules are good too, easy to use since most are setup to give a sound for a certain type of drum,combine this with the envs and matrix and you can get all types of orignal sounds. The features are great you have modulaton matrix,pitch,filter and time modulations,bit crusher,distortion,compresser and the varizer.Layering drums is out of this world with the RMIV,velocity switching and sample start points. On the RMIII I use to sometimes loose track of the kit I was using but the RMIV displays the name of the kits for you. I think there should be a way to save individual drum pad settings so that you could load up two or more different variations of the same drum type for comparing,tweaking and interchanging between kits. Also you should be able to preview whole kits and single drums while in use. One more thing is that it could use a built in sequencer like the Musiclab one in the DR008 to complete solidly. The documents are top notch couldn't be better explains every detail. The presets cover every base you can think of. I would just like to see some more up to date hiphop kits maybe some Korg and MoPhat samples. Linplugs support has always been good, the forum and newsletters are very informative. I have never had any problem out of the RMIV yet. The VFM can go two ways, if you had a previous drum module (RMIII,RM2) you get a really great discount because this is like adding drumsynths to the previous two. If you don't like the drumsynth or sample part then you could get the CM505 if you just like the synth engine or the RMIII if you just like samples. The latest update is just awesome the kits and grooves work like magic.Stability is like a rock! I have had no glitches,crashes or screwy looking interfaces yet in Sonar 3,FLStudio or Orion Plat.