Had a 32GB Esata external drive hanging around so modified it to use as C drive in a desktop. Results were so impressive I bought one of these from Amazon for my 'main' desktop. (Skip to the end if not interested in technical mumbo jumbo :)
I see several reviews commenting that the speeds are nowhere near the published theoretical speeds. As this depends on hardware, disk block sizes, physical disk size, position of file on the HDD, file access types etc my approach was 'is it better than ehat I have now?'
My main system is an intel m/b SATA II Quad processor. Disk storage is: this 60GB SSD, Samsung spinpoint 500GB 7200.2 3.5" HDD, Seagate Momentum 160GB 7200.2 2.5" HDD To compare performance I shut down as many processes as possible and used ATTO disbench32 which reads and writes increasing size blocks of data, and h2testw which writes and reads (verfies) a continuous block of data.
Results (which should always be regarded as approx as not a lab test):
Using ATTO diskbench32
With very small 0.5KB block write/read (more is good) SSD 14/16k 3.5" HDD, 3.7/5.5k 2.5" HDD 5/6k so 3.5" SD best and HDD worst.
As block size increases to more typical values, in a given time, maximum write/read speeds are: SSD 185/270K (128KB block); 3.5" HDD 107/106K (64K block) ; 2.5" HDD 47/50K (16KB block)
So as expected the SSD is significantly faster and leaves a 2.5" laptop HDD in a poor 3rd (as expected as for the same speed HDD, 3.5" disks are always much faster than 2.5" disks)
Just to try something else I then used h2testw with similar outcome although not as clear cut (read and verify 1GB continuous data )
write then read/verify 1GB continuous data is not a typical activity for me (my largest files are typically photoshop image files) but shows the SSD and 3.5" HDD have similar performance and as expected the 2.5" HDD is much slower.
finally a practical test: loading Windows 7 from 'Starting Windows' to username prompt and how long till 'catherine wheel' stops when logging in. With 3.5" HDD 30/15 sec with SSD 10/3 seconds. Couldn't test on this system with 2.5" laptop HDD but based on Dell laptop with similar startup load would expect a lot worse.
Conclusions - using SATA II interface (as I don't havea SATA III):
SSDs are much better than HDDs for most tasks but particularly when loading large files such as Windows startup and big applications such as Photoshop or Microsoft Office.
If you routinely write and read very large files then there is no particular advantage with SSD over 3.5"HDD
I would certainly replace laptop/netbook HDDs with SSDs every time (subject to cost of course.) Also I would always use SSDs for C: boot drive of desktops, and 3.5" 7200 HDDs for D: (user data and swapfile) - until of course the price of SSDs drop to the stage when a 500GB SSD doesn't cost the same as a the system its in :)