(This post is mostly obsolete to to the many improvements in FSO 7.3, 7.4 and beyond. I would seriously urge you to consider using MAPS. See here)
With FOS 7.2.0 Brocade introduced MAPS (no not the google version). It's a new functionality that is intended to replace and improve the usability of Fabric Watch. As I wrote earlier here Fabric Watch has always been one of the best pieces of functionality in FOS and I've used it ever since they introduced it al the way back in FOS 3.x or 4.x I think it was (Yes I'm that old). FW enables you to create thresholds on numerous elements in a switch or fabric. This goes from port-errors to environmental problems like elevated temperature and other hardware problems. In addition individual actions can be configured like sending out emails, snmp traps or yet even better, disable ports in case it can have or already has significant ramifications and follow-up issues in a fabric.
The biggest problem with FW always has been the sheer amount of options, menu items and CLI parameters which caused it a to be a challenge to configure it to such an extend it became useful. It is like using VI (the text editor, not the company) for the first time, you'd rather have a root canal and endoscopy at the same time but as soon as you have the hang of it you discover the sheer power of this tool and the amount of proactive management, alerts and other options will make you SAN almost bullet proof (I'm not saying monkey-proof :-)). This is also the reason that FW is either not used or configured with incorrect parameters so that it will spit out too many or too few notifications. Once again I would like to stress the importance of this great tool and the ROI will certainly double both in time and money.
So then why MAPS. Remember that Brocade is also fairly active in the networking side of the fence with the acquisition of Foundry back in 2008 and more recently Vyatta to obtain a software based networking virtualization stack. With the introduction of their FabricVision roadmap you can see that overall management needs to be synchronised and consolidated. Having 4 different hardware and software platforms (SAN, Ethernet, VCS/Converged and virtual) means this is a fairly daunting task. Brocade Network Advisor has become the management framework to handle all this albeit it is still a work in progress.
MAPS simplifies the overall management of the RAS features in FOS to more align with the capabilities across these platforms. Secondly, the number of support cases related to physical issues has increased significantly ever since the FC speeds and feeds went to 8G and 16G. 8G and 16G did not only require an update on switches and HBA's but also the requirements on cable quality changed. OM2 is no longer sufficient on these speeds. OM3 and OM4 is required for the respective connection speeds from end-to-end including patch-panels, connectors etc. Since this physical aspect of many infrastructures is not updated the increase in problems observed are almost linear proportional to the degraded quality of the physical cable plant. I've seen many examples whereby an 8G port was unable to connect and just by reducing the speed back to 4G it did not observe any issues. MAPS cannot help you with re-cabling your plant but it can help stay on top of issues that might surface.
What I don't like about MAPS is that is has significantly reduced the granularity of elements, objects and values you can configure. This might not suit every environment so conflicts of interest might become a problem. Also some settings may be converted from FW but you can't change it. This is especially annoying if you made an incorrect configuration, converted to MAPS and all of a sudden you get hit by a gazillion alerts which you then cannot modify. Also very annoying is the issue that you cannot configure different email notifications to different people. If you encounter a temperature problem you might want to let the operators of the data-centre know of this issue but when a port observes a protocol problem they don't need to know. Currently your can't change that.
I do think MAPS is currently a work in progress as previously mentioned and thus I cannot recommend to migrate to MAPS just yet. Maybe in FOS 7.3 or even 8 it has matured enough to fully replace Fabric Watch. If you have licenses for Fabric Watch I would certainly recommend investing some time in this and configure it according to your needs. The FW Admin guide is a great resource and it will certainly increase the stability of your fabric.
UPDATE: Brocade has pulled FOS 7.2.0 due to the fact it introduced so many new defects that it became more pretty dangerous to even think about running this version. As usual the x.x.0 releases should be avoided.