HFS+, like any other file system, is susceptible to fragmentation. At some point this fragmentation may impact the performance of your storage to the extent that it is noticeable. This is true for any storage that uses HFS+, including local disks (internal and external), and SAN volumes that use HFS+. If the performance of your storage has noticeably degraded over time, it's possible that it could be due to fragmentation. Some users may never notice any performance degradation.
To answer your question directly-- not all users adhere to the maintenance recommendation and they do not experience any problems. Other users perform the preventative maintenance, and have successful systems. There are also users who perform volume maintenance when forced to do so by the performance effects of fragmentation. The way that volumes are used, the number and size of the files, and how often files are added and removed all impact the cumulative effect of fragmentation. There are two facts: first, the performance effect of fragmentation is very real, and second, a new, clean file system will deliver the best performance possible, all other things being equal.
It occurs to me that you are comparing SANmp to other solutions, so allow me to make a couple points.
First, we suggest that SANmp is not deployed as one large volume, which is contrary to the way some systems are implemented. Rather, we suggest that the work space be divided up into multiple smaller chunks, the size and number of which depends upon the needs of the individual situation. We find it more flexible, reliable, and easier to maintain over a long period of time. Especially when the workflow relies on consistent high performance. Having your entire facility depend on one single volume doesn't leave much room for error-- if that volume gets corrupted, goes down or is disabled, either performance or accessibility, you've brought the entire workflow to a halt.
Also, when using SANmp with EVO (our all-in-one shared storage sever tuned for FCP, Avid and Pro tools) you get both file and volume sharing over iscsi, fibre & 10GbE all at the same time. Here's a link for more info on Evo -
http://www.studionet...m/video-san.php
Of course SANmp works with any Fibre Channel or iSCSI storage, not just EVO and vice versa.