I would like to share my thoughts with others and welcome feedback.
I have used ZFS before it appeard on OSX and used it on OSX since 32bit PPC days...
The first thing to keep in mind, is that there's been several attempts to kickstart this filesystem on OSX and even Apple intended to use it before Oracle bought out Sun Microsystems. These attempts are not a reflection of ZFS's features itself, but more so an issue of execution on the Mac OS X platform.
Articles exist on the web that suggest once you starting reading around 12TB of data on spindles, you're statistically guaranteed to have encrounted a read error. (http://www.zdnet.com/blog/storage/why-raid-5-stops-working-in-2009/162).
This is also known as silent data corruption, bit creep etc etc.
The merit of the article or how accurate the "12TB" value actually is, isn't really something that should be discussed here, but the message is clear – the larger hard-disks become, the more likelihood read errors will occur when you read/copy the data.
Think about his for a second:
How often do you replace your storage? let's conservatively say every 5-7 years. (some only do it if a disk fails)
And how long do you propose to live? let's say the "y" generation is going to reach 80+ no probs.
So, if you transfer your data every 5-7 years, that's 12 occasions (minimum) of migrating/copying your data throughout your life. How confident are you that all your data will still be readable when you want to hand down photos of loved ones or movies of your children?
If you're not storing your data that can be guaranteed consistent-on-disk by using block checksums, you may want to rethink a few things.
Also, what I'm talking about here has nothing to do with backup strategies – that's another topic for discussion another time, but realise that if you cannot guarantee consistency-on-disk, all you're doing is potentially moving a hidden problem to your backup strategy.
This all sounds fairly drastic and harsh, and this issue is essentially masked by current disk sizes, but with 6TB drives available, it's something you might want to carefully consider for the future.
Being able to use checksums to verify your data is just one of the many features of ZFS, there are many more that no other filesystem can offer natively on OS X and so it's for this alone that I rate ZFS so highly.
HFS is should've been retired years ago, (http://arstechnica.com/apple/2011/07/mac-os-x-10-7/12/) Even Apple know this by there decision to adopt ZFS back when Mac OS X 10.5 was being developed.
How do you feel about your data sitting on HFS now?
Hat's off to the guys developing ZFS on OSX, you guys rock!