"We have easily updated some Lenovo Thinkpad T61P and Dell Precision M4400 at work with an internal SSD. In both case you just need a screwdriver and in 5 minutes you can substitute your HDD.
I can say that the performance are stunning compared to the previous disk. The boot is really fast and also the launch time Visual Studio 2008, SQL Management Tools and office applications like Lotus Notes, Word, Excel is reduced.
I did some benchmark on build times, but we don't have a big project with thousand files, only many small projects with hundred of files. In any case I measured a performance increase by 25%.
I did some benchmark on some queries on a local database and in this case I found an increase of 50%.
Pay attention that with XP the performance with SSD decreased in time, you need to wipe the cell with a program from the manufacturer, time to time.
Buying an SSD for external USB 2.0 drive is a waste of money. With USB 3.0 things are going to be interesting."
"USB 2.0 claims to support data transfer rates up to 480Mbps, and SATA II (Let's say you want to compare with Internal SATA II) claims to support data transfer up to 3.0Gbps (using 10/8 bitstuffing – actual “throughput” is lower). Sata III is 6.0Gbps....
If it's an external HDD for backup or storage, USB 2.0 is way ok."