I am toying with purchasing a 2nd PS3 as a "Bluray player plus" for the downstairs living room.  My current plan is to wait until after E3 to see if there will be any good console bundles announced.  I know that most PSN games can be on both systems at once.  However, I have heard there are some problems with game saves on many disk games.  Some are open, some are locked to your profile, and some are locked to your actual machine.  Do a large number actually fall into this restrictive 3rd category?   
 
How well does using your account work across multiple machines?  If I try to sign in downstairs while the upstairs machine is on does it disconnect my profile on the upstairs machine or just deny the PSN log in on the downstairs machine?   
 
Are there any other multi-machine issues that I need to know about or look out for?   
 
Thanks

I find it easier just to buy an extra hdmi cable and just unplug my ps3 and move it to another tv if i want to use it for playing movies on my bigscreen.

well you can take the hard drive out of your old on and put in your new one. then you uncopyible save will come with you

Almost all PSN games can be used on up to 5 ps3s. There are only a few that dont and the one that comes to mind is warhawk.  I haven't tried logging into the same account on two machine but i assume its the same as with the xbox 360.

" I find it easier just to buy an extra hdmi cable and just unplug my ps3 and move it to another tv if i want to use it for playing movies on my bigscreen. "

" well you can take the hard drive out of your old on and put in your know one. then you uncopyible save will come with you "