For anyone looking to offload/backup a large amount of data, this one is worth considering.
I bought this a few months ago (paid £200 for it ) and it performs a lot better than I anticipated. It writes individual large files pretty quick, sustaining over 100MB/s. Smaller files write slowly much like a USB flash drive, typically in the 10s of files per second.
Read speed is much like any other hard disk, i.e. 100-150MB/s depending where the files are located on the disk and similar seek times to a hard disk. In turn, it's fine for storing photos, video, etc. as these all preview, open and stream just as well as any other hard disk.
The two front USB ports are USB3.
With this price, this works out as follows in comparison to optical disc formats:
37.5p per 25GB - Single BD-R
75p per 50GB - Single BD-R DL
£18.75 per 1.25TB - 50 spindle of BD-Rs
7p per 4.7GB - Single DVD
£7.05 per 470GB - 100 spindle of DVD-Rs
Of course the downside is that if it fails - everything on it is lost, unlike discs where just the affected discs are lost.