FreeNAS is well suited for most storage serving scenarios, whether it be for an office file server, backup destinations, data replication across the internet, or as backend storage for virtual machines. It can serve various types of clients via a plethora of standard protocols and can easily integrate with existing infrastructure using LDAP authentication and so on. It's pretty simple to use (it helps to have at least a basic understanding of the underlying technologies) and almost maintenance-free. One scenario that springs to mind that it may not be appropriate for (yet) is as S3 storage. However, S3 functionality was added in a recent release and may have improved greatly since then. I'm sure it will eventually work very well for this.
We use it for every linux service we need to have running. It really works great and is easily manageable with the SUSE Manager, which helps a lot with the updating process. Although it is not stressfull on the CMD itself, it really does simplify things. Besides that, we are really happy with working with SUSE Linux Enterprise Server.
The support window for service packs after a new SP is released is too short.
Community engagement is low.
There are times when supported packages fall too far behind and create compatibility issues with applications. The Open Build Service usually provides a way around this, though.
We've been using this OS for about 8 years in a productive environment. During this time, we have never run into any problems that stopped or impacted our production environment. We have been able to solve any problem we ran into using either common sense, suse documentation or suse support.
Support personnel are helpful and fairly fast to bring resolution to non-emergency issues. Patches are created and posted in a timely fashion. We so far have not had any major problems that needed support
FreeNAS effectively uses all resources really well and it is highly recommended for in premises NAS. It has unlimited ROI as it is really free and open-source. The only payment we need to pay is when we need any support from those guys. FreeNAS helps us to effectively do our work with the legacy systems as it manages all the components really well. FreeNAS although rebranded to TrueNAS will still be there until our legacy systems run.
We went straight to SLES when we initially started migrating oracle to hana since at that time, HANA came on a pre-installed server that had to be purchased from an official vendor, and SLES was the only allowed OS. We stuck with SLES after we became certified to do our own installations because so far, SLES was a good fit for us.