Having tried OpenSUSE 11.04 and been very impressed, I'm not exactly sure where the extra "professional" value comes from. While it was under Novells wing, it benefited from the Microsoft / Novell deal in terms of being protected from the vultures inside Microsoft's extortion racket department. That in itself wouldn't be an issue for me, but I'm guessing that's not the only edge they have. Through that deal they'll have extra knowledge and access to Microsoft's Sharepoint, Exchange etc to make them more compatible.
The problem is that Microsoft have done to Novell what they've done to others, and are in the process of doing to Nokia, they've cored them out from the inside and left them a husk with pariah status, and their only options left are to sell off the assets. OpenSUSE is an excellent distro, the SLED part has been split off, or is in the process of being split off to stand alone, I have no idea if that's acceptable to the OpenSUSE people, or whether they want to split off and go their own way. In either case, how does that apply to any special functionality SUSE got from the Microsoft deal? Will they have to revert back to the same as other distros to stay legal? Does it only cover SLED now, not OpenSUSE? I have no idea.
RedHat work on the idea that they can convert a CentOS install over to paid support RHEL at any time with a simple change of repos. I'm guessing Novell had a similar thing with OpenSUSE to SLED, meaning you can install OpenSUSE to see if it's what you need and try to support it yourself, but have the backup option of calling in Novell / RedHat to provide professional support should the sysadmin leave, or you just want an extra level of safety cover. Other distros are going to be harder to match that, with the possible exception of Ubuntu.
My suggestion is that if you want the safety blanket of being able to switch to paid support, then either CentOS (even that seems to be dying now), Scientific Linux (the RHEL clone most of the CentOS people have all fled to). For me the current state of flux around Microsoft / AttachMATE / Novell / SUSE would hold me back until the dust settles and we see what the outcome actually is. If you're comfy with supporting it yourself, then perhaps Debian Stable, or an Ubuntu / Mint LTS would be a better bet. There's every chance that supporting it would be pretty straightforward, but time is money in a professional environment, when it goes down, it needs to be back up ASAP, those are the times when you really appreciate the paid support safety net.