Summary: I made the choice to purchase the Rikiki 1 TB portable HD after reading many reviews about it and comparable products. I have been very happy with the device after owning it for ~6 months. The ease of installation, quietness of the drive, and the streamlined design make it ideal for my application. I use it to back up two different machines - leaving it plugged into my iMac usually, but occasionally backing up my MacBook Pro. The drive case stays cool all the time.
Summary: If you are on the go and need lots of memory without having to take lots of extra baggage than this is an excellent option. I use it to store and back-up my photos while in the field. I have even formatted it so it can be read and written to using both Windows and Mac, very convenient for sharing files while on the road.
Summary: I wasn't at all worried that this wouldn't be enough extra memory- still I am very happy that I was able to put everything on my new external drive and have room to spare! I got this as I had run out of room on my MacBook Air for my music library (several thousand songs...) and was able to transfer it all easily.