SSD on boot is a luxury ?
its nice but not needed
NOW when OSX swaps its very nice cause its going to be much quicker
now having my boot on SSD I wont go back !!!!
on the boot its more about getting to the spot and getting that program off and into memory and SSD blows away any mechanical disc
the same reason they are so nice in Cache situations like for Lightroom or Bridge
head over to sites like anandtech and others and look at the random reads the seeks and the I/O of SSD and you will see they are so amazing
also note not all SSD are the same as mac users I think we should stick to a few and some searches here will bring those up but the Sandforce options might be the best bets
so OWC or Vertex 2 or the Gskill phoneix pros
with those 3 choices I think for photographers having your boot on a SSD and your cache files if you use LR or Bridge are worth it ?
LR or Bridge cache are not scratch

the thrashing and killing of a SSD used for scratch is unknown I think ? not sure if its worth it trying to do some time testing later and decide if throwing away $100 on a 40 gig SSD is worth it ?
this is if you make your living on PS work and can say well saving 4 hours a year is worth it
so for me if I am working on 100 files in a row and I can save 30 seconds a file sit and do nothing time its going to be worth it !!!!
so far last night I did a job of 50 images and watched my waiting for PS time and tomorrow my next job going to switch back to to my regular scratch and see if I notice any sit and wait for PS time ? if I dont notice any that about answers it for me
so my old short stroked raid 0 scratch might be the better option still for my scratch ?
I wil try it back and forth a bit and decide if its worth it to test farther ? if I cant notice something chances are its not worth testing ?
I have a set action to run when opening a image to edit it lays down a burn and dodge and contrast layer I can then quickly move across and adjust to get my base image ready for more ! now its instant ? I open the file it pops in ? my old setup took 2 seconds so I went about thinking how to make it quicker !
I notice in LR the biggest complaint is waiting for the sliders in Dev mode so I did a ton of testing and found SSD and putting the cache on SSD got my sliders working in about .52 seconds vs .79 for a short stroked HD so that might not sound like much but in real sit and wait it was worth it !!! thats a real world example of SSD use that for us photographers will pay off !
so boot yes !
scratch ? at this point NO keep doing short stroked raid 0 setups of at least 2 discs ?
LR and or Bridge cache YES !
LR catalogs ? no keep em on a raid
files keep em on a raid !