RAM drives have pros and cons.
Pros.
■ They are fast. No really, they are fast. If you want to have extreme disk benchmarks scores they are the way to go. But as far as improving performance goes you are unlikely to find that a RAM disk does much for you in the real world. Storing browser caches on the RAM disk will speed up page rendering from cache though, so that's a good thing.
■ They are more secure than storing data on hard disks. Want to get rid of your personal data from web browsing without leaving any traces? A RAM disk can do this for you. After removing power all data stored on it is permanently lost unless you dump it to the hard disk at shut down.
Cons
■ If you use it for, say, games, you'll need to have the system copy the game data from a HDD to the RAM disk after every boot. This can take an extremely long time depending on how fast your HDD is and how much data is being copied. For web browser caches this is not an issue as they are recreated whenever lost.
■ They have a low capacity. Unless you run a server board with 24GB of RAM you're not going to fit much onto your RAM Disk. As far as OSs go you could probably fit Windows 9x or most Linux distributions on a 4GB or larger RAM disk, but forget any newer Windows OS as you probably don't have nearly enough RAM.
You'd be better off with an SSD. It's not quite as fast, but does not have the most of the downsides of RAM disks. As it is permanent storage you'll want to use the Ram disk for securely destroying browser caches on reboot/shut down still. You only need a small RAM disk for this. I have no idea how you'd boot from a RAM Disk. You'd need to copy all of the OS data from a HDD to the RAM Disk at boot or have a RAM Disk that is constantly powered (risky as a power outage means you kiss your OS goodbye).