There is a falloff!
I have a 5GB library (not including the 11GB of baggage files.)
Example- on my laptop with its 25MB/sec hard drive searching "jn 3 16" takes 32 seconds to complete.
On my desktop build project with the Core i7-920 and 12GB ram:
On an SSD array that has 584MB/sec read rate, the same search takes 8.4 seconds.
However, making a 5.5GB Ramdisk with a read rate of 4,234 MB/sec and loading the non-baggage resources there, it still takes 7.8 seconds!! So even thoug the read rate on the ramdisk is over 7x that of the SSD array, it only picked up less than 1/2 second of speed!
The raid array was 4 Intel 80GB X25-M Generation 2 SSD in raid 0.
A study of this drive in showed less return for your money on read rate beyond 2 drives (going form 3 to 4 drives not as big an improvement in read rate, but write rate (for windows swap file, etc goes up with each drive.)
So, 2 of these drives would be the best bang for the buck which would be around $450 if you find them fast enough at good ebay pricing.
I should point out that new firmware for the 160GB model X25-M Gen 2 boosts the write rate from 70MB/sec to 100MB/sec (the firmware upgrade did not boost the 80GB mode's write rate from 70MB.) So you could get even better write rates with just 2 160GB models, but they cost more than twice as much and you might do better with 4 80GB raid0
Next I went to processor speed.
Bumping the cpu speed from 2.6GHz to 3.6GHZ lowered the search from 8.4 seconds to 6.6 seconds. Now we see the effects of horsepower on the search engine.
The RAM was running at 1066MHZ. Boosting ram speed to 1600MHZ lowered the search time to 6.2 seconds.
I cant overclock anymore without a lot of voltage tweeking which takes a lot of time.
I wish Libronix had a 64-bit version. A tech said its a ram hog so it would be interesting to see what throwing 12GB at it does.
I might get around to trying to install the program to ramdisk to see what that does.
For the laptop crowd, there are some (but $$$$) laptops that take 2 harddrives (or SSD) where they can be raid0.