With dual-drive setup, you can do the split. Running pure OS X off of a SSD boot disk is more than sufficient. Should even leave room for your Applications folder. I personally left also the Admin's home on SSD just in case I need to boot and log in with HDD inoperable.I actually have more than 200GB on my Mac OSX Partition, 60 on my Bootcamp so 120GB is no where near enough for me
All of the users' homes (the /Users folder, containing your Audio, Movies, Photos, Other) you can move to HDD.