Have not been impressed at all with the off the shelf offerings ie nomad, armadillo etc. Mostly look like clusters.
Have seen two or three really well set up systems but these have been long term developments of the people involved.
One in particular from Hans Kessler in Switzerland.
http://www.swiss-cave-diving.ch/PDF-dateien/Sidemount-HRK.pdfTrent Lee, CDAA science officer, has a well thought out minimalist rig for really tight situations.
Andy Higgins also has a really streamlined setup.
The common factor in all these rigs is the utilization of hogathian principles in the design and operation.
Seems to me that to dive a sidemount cluster, as a lot of them seem to be, defeats the purpose of the whole exercise.
As with most things should be a tool for the job, but as with rebreathers, seems to just be latest flavour of the month.
Used mostly by tools too lazy to keep their fitness up to dive backmount. Sidemounts in mostly vertical cave structure like Pines, LOL.
Can't wait for the PADI introduction sidemount quickly followed by sidemount advanced,
sidemount master, sidemount elite, sidemount super elite to begin.

Cheers