There seems to be lots of controversy about Agrellan Earth... apparently its not working for people and GW is saying its a bad batch. The GW I purchased mine at now says that they are out of stock, which I think means they pulled it off the shelves. Anyway, I was able to get mine to work and have posted a picture below of what I was able to achieve.
Blood for the Blood god:
Basically a deep red with gloss medium. Handy to have in a pot and ready to go, but nothing you can't mix up yourself. If you plan on using a lot of this then its probably worth it, but if its just for the odd guy you can do it yourself. Nice red colour.
Great patina colour in a wash consistency. I really like doing patina finishes on models, and this will work great for that. However, you can mix this up yourself with some blue-greens and matte medium plus water. Worth it if you like the convenience, but easy to substitute.
UPDATE: I've done a video review of this showing how it works compared to how I did it previously, it can be found here: http://itslikewatchingpaintdry.blogspot.ca/2013/12/nihilakh-oxide-demo-video.html
A crackle paint for doing dessert like earth. I don't really like this effect on bases, and you can get much more variety from a craft store. Unless you specifically like this look (it only comes in one colour) I'd pass.
UPDATE: Here's a picture of what I was able to achieve. You have to put it on really thick... About as thick as white glue when putting down sand. I wonder if it would help if you did it over a gloss coat.
Nice light green with gloss medium. If you were doing a nurgle army and wanted lots of puss this would be worth while, but otherwise its use is limited. Maybe Tyranids too... but some gloss medium, green paint and water will do the same thing.
A wash consistancy with very fine grit. This stuff will be great for weathering metals and vehicles. I'm not sure how else you would get a similar effect (maybe mixing powder with a wash?), so I think this one is a winner. I'm looking forward to using it on Skaven, Orks and Ogres.
A drybrushing paint (orange) that goes well over Typhus Corrosion to make a rusty effect. I like this, but if the budget is tight you can get away with using a similar orange paint. The technique they describe will save time, but unless you're using a lot of this it might not be worth the investment.