The system runs fine & everything works good. About the only thing that I could think of I would want would be native support for the Fuji X-T1 that they say is now out there.
This is an issue with any mac system, as you add a camera, you add a software suite that sometimes requires a system upgrade.
I have macs in every system from 10.68 snow leopard to maverick.
I believe 10.68 is the most stable of all mac systems, though not the fastest.
10.75 is ok, though not a huge leap to maverick, but not all programs run effortlessly in maverick as many have mentioned.
Personally, the very best way to decide on a new system is to buy a 1 or 1.5 terabyte lacie rugged or similar pocket drive, format it in disk utilities in mac extended journaled.
Then buy carbon copy cloner, syncro x and do a bootable clone of the disk. You can also do this in disk utilities (read the mac forums).
Then once done, change your selection of boot drive to the external drive, and run every application to make sure they operate properly and you clone is working.
One this is to keep all your program serial numbers on a simple text style document so if the cloned programs won't operate you can copy and paste the serial number.
Also it is good to use your 10.75 install disk or folder to add all separate extras (utilities).
Then and only after using the clone as a boot drive for a period, upgrade the boot drive to see if it operates for you.
Actually, this is not a bad way to upgrade your computer and use the newer software only when needed on a higher os.
Please take what I say with a grain of salt because every system is slightly different on every machine, every machine has different programs and user preferences along with uses.
My rule of thumb though is don't change unless you have to, never because you feel you might be missing something.
I've been a mac user for a long time and they tend to beta test though their users. I've seen important computers go down from apple upgrades, from java, to itunes to full os changes.
Anyway, once the upgrade works on your cloned drive and you feel the upgrade was worth the effort then you can upgrade you installed boot drive.
Though as most people say, give it at least two point upgrade cycles before even thinking about changing your complete system.
Always err on the side of safety.