I have just receved an OCZ Agility3 120gb ss. I am thinking of installing it in my laptop for work for the next couple of months and then moving it to a desktop I use in the winter. Will this effect the drives performance?
The SSD won't run as fast on a SATA II connection, but it will run.
You can run it in the laptop for a while, then transfer it, yes. You'll probably have to re-install the OS on it, because the desktop will need different drivers, but that's not difficult. It might be smart to do a Secure Erase on the drive in between, to ensure all the drive data structures are reset.
If you are running Windows 7 on both machines, then the drive's performance should be affected (Windows 7 supports TRIM).