For a free product this is rather good, actually I'll go a bit further and say very good.
The 8 pages are bursting with horrible illnesses from the deadly to the inconvenient and it suggests quite a lot of research went into putting it together. More than one might expect for a free product. Then again I noticed the reference to the fact that the product is actually taken form the horror RPG “Haunts and Horrors” which I have yet to acquire (I'm told by those that have that H+H shows a lot of research went into it, so that probably explains this products depth, given it's short page count).
One or two typos have snuck in under the radar (I think – English is not my first language), but I don't find that a big problem.
Although it could be used with just about any game, some legwork will be needed by the GM to make it fit anything other than the Gethsemane Games Engine used in their RPGs. However, if you do play other GG games this is a good little addition. Personally I'll be using it in my “Spelldancer” sagas to good effect. Although Spelldancer has it's own disease section, and the rules governing disease, treatment and recovery (or failure to recover!) are the same, the actual diseases don't double up with the ones in the Spelldancer rules with one exception (Gangrene, although it is given a different name in the Spelldancer rules).
The product lacks much art, but for a free product that isn't much of a surprise – besides I print most my PDFs out and with ink costs here being so steep (oil is cheaper by volume) this is a good thing for me.
If you want to add the element of illness to your games, I recommend this product at least as a starting point.