I have 30+ games and am a PS3 owner with a 320GB HDD i bought off amazon cheap for £30...
I have all my games installed (well at least the ones that use the instal feature) and still have oodles of room left that i casually fill up with demos and trailers, because i don't know what else to use it for.
I'm sure if MS didn't charge extortionate prices for their HDD Rotmm, you could easily pick up a 500GB HDD and install all your games to your HDD.
The issue sounds more like available HDD space than an issue with installs themselves... manditory or not.
I'm sure that now every PS3 comes with a 120GB HDD or higher (I bought my bro a 250GB PS3 for £199 recently), far less people will complain about manditory or optional installs.
I certainly don't mind em' as long as they don't keep me waiting unecessarily long on an install screen.
I do like the sound of the "pre-designed" manditory tutorial/stealth install though
Any devs on here know how realistic something like that would be to impliment?