I am in need of an external hard drive for backups of my new 24" iMac due to arrive on Wednesday March 25. I am moving from the PC works (old Dell) and will need something larger than the old one I have for the long term. I have an old external hard drive case and a 250GB ATA hard drive inside I can use for the time being with the new Mac if I reformat it. That said, I would like to get a drive that is at least equal to what is in the iMac with is 1 TB. I have read a lot of postings and believe I will get a Western Digital MyBook for Time Machine backups (unless someone has a better alternative). Is there any reason to get the Studio 1 or II (FW 800) over the Essential (USB 2.0) for my purposes - backups only? The price difference is $40-80 for equivalent drive space with connections being the difference. If anyone can provide feedback it will be greatly appreciated!