I have expected some concern over RAM use and duplicated libraries. I myself wrestled with it as I was getting back involved in using a self contained approach, and I am finding the theory of it paints a much darker picture than what the reality is. At first, I expected a much larger cost in terms of RAM and disk space than what I have actually been seeing upon experience.
Out of curiosity, I did a quick side by side test today of an scm-only system and a tcz-only one, with some of our popular and larger apps to see just how much difference we can expect when we open up many apps at once. Both systems were booted with only loading these apps and their deps, as well as icewm. Here is the list of apps that I installed and launched - Xchat2, gqview2, leafpad, transmission (gtk2 for tcz, gtk3 for scm), opera-11, midori, audacious (gtk2), audacity-1.3, epdfview, emelfm2, gimp2, geany, pidgin, minefield9, gtk-gnutella-gtk2, foxit-reader, and geeqie. I opened the apps, and then cleared the memory cache. Nothing scientific, but able to give a general idea. Transmission-gtk3 is a gtk3 app which also brought in gtk3 to ram for the scm install which made a larger impact on the scm system than the gtk2 version would have, tcz install used gtk2 for transmission which is also shared among its other loaded apps.
Ext type total RAM total "du" size of /apps
used at idle or /tmp/tcloop
tcz 333mb 271mb
scm 326mb 360mb
The total size of the scm files could be trimmed more, but they seem to hold their own in the memory use dept, at least on first launch. I am not saying anything bad about the tcz, and there are many little factors that go into how much ram an app uses when launched. But I am just throwing some numbers up to give folks an idea of expected system impact before they rule out an extension type before they try it.