You wont see much differents when using only 250mb of ram, thats why they say to use 512mb with systems <= 2 GB of ram. At 250, thats just for system files I would bet, so you wouldn't see any or little boost from your programs as it is.
Not at all actully. Actully it would "cost" more as you have to keep the HDD spinning and drawing in power like crazy. The reason disk stop spinning is for safty. What happens if you have it running like that and your little brother came in and push the tower over... will not much actully. Why? The disk wasn't spinning. Now take that same seno and make the disk spining. The arm of the HDD would jump then slam back down on your disk causing all sorta of damage as the disk keeps moving trying to get the data you wanted... There went your HDD and your data....
As it is, HDD and SSD will have a limit to how much data they can spit out at random times, this is called random read and random write. This really isn't effected by the spining as alot of people may think. Actully its caused by how far the arm has to go too get the data. As for SSD, this is effected by something called channels, the more you have the more data can be push out the door at random times (I could be wrong on this one, SSD are a new tech). So at max, maybe it will save about .2-.5ms or a little around 2-3MB witch isn't much for the cost of it having to spin. Now this is random not sequential access.
Sequential Access is where both SSD and HDD shine! Its where you read data like you would a line of text, instead of having to jump around for all the words for at line in a book. Even here they are cap at 50-120MB for HDD and (while still new) SSD can hit the 300MB mark easy.
OCZ Vertex:
1. Turn off pagefiles, any auto defrags, "Enable write caching on the disk", "Turn off hark disks" (You may change this one to 30min to 1hr to save some power but is not needed on desktops, only laptops.
2. Sat the allocation unit sizes as they say when you format.
3. Other little details that I dont remember..., but are on the OCZ Vertex site.
Reason for this is, you want to lower the number of information the SDD has to put in its channels like I said above. If the channels are all ready busy with caching and looking for information, then loading will take longer as the program has to wait for a channel to open or have to use only one channel (witch is 1/4 of the data stream access). As for the power, you dont have to turn it off, but if you do; the system has to wake it up from "sleep" and thats where you get slow down, not data access. As for the allocation sizes... that has to do with something on the SSD chips them selfs... like I said too, its new tech so I dont know all the details, but i'm perty sure on the ones I know.
Also... RAM will always be faster then HDD or even SSD due to low latency and push rate at the 1GB mark vs the 50-300MB of SDD and HDD...