We have tended to think 'Google' in most of our consideration of SEO compatability mainly because its the logical and most sensible thing to do - especially as it is the most popular search engine used.
However, like us, most people probably take those requirements and expand them into thinking about the bigger picture - yahoo etc too.
Basically, if you can conquer Google then there is every chance you will be taken seriously by your customers too.
A well designed and properly created site that is trying to impress search engines with its superb content will impress all interested search engines... not just Google.
SEO in itself holds many arguments - even whether or not there is any point in really working on the natural listings at all is one argument that certainly holds true for some (but not many) businesses.. and PPC is all important for others at any cost.. and again, the most successful PPC is also Google...
I have spoken to people that have spent a fortume with SEO companies to no avail... and those that will only ever spend on PPC and vice-versa... but Google is always high up in the conversation of SEO aren't they?
You just have to decide what is most important for your particular business within the time-frame allowed and budget available... but Google almost always figures in that somewhere.
- so, it seems.. they probably are 'all that' in many ways
