There will be generally two types of people considering buying this: 1) died in the wool Eels fans (of which I am one); 2) people new to the Eels sound.
If you are in the first group, there is not a great deal on this that you will not already have. Most of the twenty four tracks are from the albums (Beautiful Freak, Electro-Shock Blues, Daisies Of The Galaxy, Souljacker, Shootenanny & Blinking Lights And Other Revalations) but with a couple of interesting little additions. There is a Jon Brion remix of 'Climbing To The Moon', rendering it more melodic. Midway through is a bizarre but excellent version of Missy Elliot's 'Get Ur Freak On'. Works surprisingly well! A live version of 'Dirty Girl' breaks up the studio sound nicely, followed by the Shrek 2 song 'I Need Some Sleep'. These do all come together nicely, giving a compact review of the band's work so far.
If you are in the second group, this is probably perfect to get you into the singular Eels sound. Some people may have been put off by the darker sounds of the first two albums, or the seeming mis-match of almost pop tunes with distinctly un-poppy lyrics towards the later albums. However this takes you on a tour de force of the repertoire displaying the brilliance of the band for all to see!
A word to the wise, though: The DVD of music videos is in the American NTSC format, which wasn't displayed on the page (at least when I ordered it). Should be ok on your PC, but unless you have a NTSC compatible TV, it will come out in black & white!