A few more thoughts:
1. Probably the key feature with DeviceNet is that it is a 100% open system, and is not tied to any one vendor. Indeed I have put together DNets with not one single AB component in them. The other key feature has nothing to do with the media, but with the far more powerful idea under the hood...CIP. Check this out:
http://www.ab.com/networks/CIPwhitepaper2.html
2. CompoBus/S is in fact Omron's in house version of DeviceNet. I am not sure why they went down this path of taking an open system and making a proprietary version of it, but hey it's a big world.
3. Profibus is well established mainly due to the sheer weight of Siemens presence globally. It uses an older far less efficient messaging scheme and largely relies on very high baud rates (12 M) to get adequate response times. By contrast Devicenet gets similar results trundling along at 125k, 250k, or 500k.
4.Also Profibus DP doesn't handle peer to peer messaging very well, so it isn't easy for example to set up say a PanelView and a VSD on the same network and have the PV act solely as a display for the drive, with NO PLC in the network. The upside of Profibus is that because everything is less flexible and more tied down, it is easier to get going if you can't be bothered reading the manuals.
5. Remote I/O is AB's older proprietary I/O network...not a contendor for anything new these days.
6. ASI is a neat system for pulling together simple I/O devices in a very low cost manner. It has the merit of simplicity and low cost, but for anything more complex it has limitations. As Doug suggested some people get around this by using DeviceNet as the backbone and ASI as a "dropline"...
If you are old enough to recall...all through the 80's and 90's the customers asked for "open networks", "vendors only lock us in with proprietary systems", "we want a single network standard"....and yet when RA devised a perfectly acceptable open network, and made the specification open and non-proprietary, the response has been less than stellar.
The fact is that you can have an open system that has all the features everybody wants, offers full interoperability with every product ...but requires the user to read the manual at least once...OR you can have relatively closed systems with fewer options and less flexibility that are easier to configure.
PS panicmode. I haven't assumed an AB processor anywhere in this thread...the original question asked for DeviceNet information explicitly, not a comparison with every other network out there. That is just far too big a topic for any post.