What is your opinion on Webmin and YaSt?
Webmin is nice, but is, in my opinion outdated. Webmin does offer a lot of modules that you can add, and it’s light. YaST is nicer and more complete in my opinion, but YaST is not distro neutral like webmin is. There is also now webyast. Webyast does the same ting as YaST bt via a web interface.
As an openSUSE user i only need YaST because is the most powerful control center around. Webmin is good either if you use a linux distro that has a different or no control center at all or if you are a system administrator. As an universal web interface to any linux distro it has my vote.
Never used Webmin…however, in any large deployment, I wouldn’t use either.
You cant ignore Webmin.In fact,it gives more control over your system.
Mixing config tools can be risky. At least it was years ago. I use yast exclusively when configuring OS. Yast runs scripts that expect things to be changed via yast. If you start making changes in other ways, you will likely get one of your config tools confused. Not to mention confusing yourself.
It’s been years since I got into the innards of this stuff, so I could be wrong about how things are today.
hattons: you are right it is very risky. Personally, i dont feel the need to use other system tool under openSUSE beside Yast or WebYast. But for a linux distro like Debian, Ubuntu or Linux Mint (distros that don`t have a control center like Yast) i highly recommend using it. I have used webmin under Debian in the past and the system did not have a single problem. The right tool with the right experience can make all the difference 
YaST1 or YaST2?
if the Selection is YaST1 I will take Webmin, if it is YaST2 ill take YaST2
Wait till you see YaST 3. 
I guess i am too “Old School” For YaST 3
I doubt it since YaST 3 is quite out yet. Read this; openSUSE News