Treebore said:
CSIO is the best City supplement I have seen since the Waterdeep boxed set. Fair amount of detail, legal system, fleshed out adventure sites, excellent locations index, nice small maps that you can still read. Very worth getting for a "main" city setting. Plus the Wilderlands specific stuff is easy to edit out, just ignore it.
Oh, I know the general atmosphere of the city, because I have the Player's Guide to the Wilderlands, and there's definitely no need to cut the setting out, because I like it

. Personally, I'd just like to get rid of some real world references (god names and the like).
I'm just waiting for USPS to stop sitting on my copy

.
Acid_crash said:
For my own curiosity, what is CSIO? Also, can anybody tell me more about Arcanis? I have actually never heard of either of these so any links or info would be great. Especially since CSIO is a city supplement.
CSIO stands short for "City State of the Invincible Overlord". It's the most developed part of one of the oldest settings ever done for D&D, that's the Wilderlands by Judges Guild (redone by Necromancer Games). The city supplement is renowned to be one of the best ever done; I can tell you whether this is true as soon as it will finally arrive at my doorsteps.
Arcanis is a setting by Paradigm Concepts. It's a fully fleshed out setting with remnants of a "Roman Empire", an oppressive religious state and lots of other, rather diverse regions to play. It's connected to a "Living Campaign", similar to Greyhawk, and seems to be alive and kicking

.
Edit: You asked for links

. It's funny that the best description of CSIO is on the White Wolf order page
here and not on the
Judges Guild Page 
.
As far as Arcanis is concerned, try
this link. The website is terrible, btw. I can't tell you much more about Arcanis, because it did not really click with me.