I've always had a little bit of a soft spot for SuSE, and I had my fingers crossed that when they were acquired by Novell, it would become more popular in the business world.
I think two main things are holding it back from becoming one of the 'main' distributions. The first is YaST, which is just strange in the land of yum and apt. The second is just the sheer amount of support distros like Ubuntu have. There's not as many resources out there, even though the last time I checked OpenSUSE had a strong, but small community.
YaST is not comparable to yum or apt. YaST serves as a general OS configuration tool, sort of like "Control Panel" in MS Windows. While YaST can be used to install packages, packages can be retrieved from the command-line using "zypper" which functions similarly to apt-get and yum: http://en.opensuse.org/Portal:Zypper
I'm not really sure what you are referring to with "support". If you are referring to the sheer size of the community, Ubuntu does has a larger community and also benefits from the fact that most Debian-related/Ubuntu-derivative related docs/advice apply to Ubuntu as well. It looks like openSUSE has a fairly active community forum: http://forums.opensuse.org/english/
YaST vs yum/apt is technically a wrong dichotomy, since YaST (as a package manager) is just a graphical frontend to zypper, which is pretty much like yum and apt, just with its own syntax.
I know that many people dislike YaST, yet I have never understood why. The point is that you do not have to use YaST, you can edit every config in the normal way with your favourite text-editor, you can do everything via scripts, you can do everything headless etc.
YaST is a nice bonus, but openSUSE offers the same thing everybody else offers in terms of non-gui tools. Just from personal use patterns, I sometimes use YaST for convenience sake, the user editor is nice, and so is the bootloader-stuff. Can I do it differently? Sure, user{mod,add) etc. work just as well and might be preferential sometimes, the point is that both work.
I think two main things are holding it back from becoming one of the 'main' distributions. The first is YaST, which is just strange in the land of yum and apt. The second is just the sheer amount of support distros like Ubuntu have. There's not as many resources out there, even though the last time I checked OpenSUSE had a strong, but small community.