I don't find it at all a challenge to use OS9 for most tasks... as mentioned earlier in the thread, I use my (admittedly slightly tickled but still thoroughly obsolescent by 3 hardware generations) 9600 very regularly with 9.2 and a modest G3 upgrade. Realistically under 80% of situations it does anything I would expect of the G5 just somewhat slower... but even in saying that, it isnt a huge arrow to the knee given that the G5 has 6 times the 4-5 times the RAM, bus bandwidth and raw processing speed (not even accounting for the inherent improvements in actual architecture... Obviously the 9600 would be slow as balls if I were to run 10.2 (which is installed and possible to boot from but I have zero inclination to do so as if I wanted to use a totally abandoned version of OSX I can boot up my iMac's, Yikes, G3, or Sawtooth), but under a "classic" operating system and running software designed for it, it is capable and pretty damn fast.
For what it is worth I could theoretically use it for everything and it wouldnt really be too much of a problem, as there are legacy applications that do thye job well for any productive task i might need to undertake, and Classilla makes for a very capable web-browsing platform. That said, Youtube is a problem and certain modern pages are very resource heavy or just dont play well (TC forums for instance, operate terribly in Classilla). And add to that my entire 2 and a half week long music library is stored on my hard drive, and while this would be theoretically possible on the 9600, the 36Gb cap on SCSI hard disks would make it impractical to store all my music locally, and whilst using a firewire drive is an option as it has a firewire card, it is messy... vs just tossing a pair of 500Gb HDD's in the G5 and never having storage concerns for another 10 years.
As for the G5 itself, I consider it to be a fairly pedestrian feat using it as a daily machine. The only issue (if you can call it an issue) I have encountered is the inability to use Skype as of last year, which isnt a major concern as I havent used it in years as I always hated how slow and buggy it always tended to be in it's early days, and Australian telecommunications infrastructure is crap anyway so connection issues always made the experience suck. I have Skype on my iPhone anyway and I still dont use it. The only other major issue is the inability to back up my iPhone to the G5 since iOS 7 reuires iTunes 11 which is unavailable for PPC... again this is an annoyance, but can be worked around by either buying a $50 Windows machine for the task or going PCless and using iCloud. Aside from these two issues, using my G5 daily is really no different to using my housemates 3 month old laptop, except that the user experience is IMO, nicer on my Mac. Speedwise, there is really no difference, and there is an older version of a commercial app, or an open-source or freeware sollution to almost everything I will use the machine for. I could buy an iTrashcan tomorrow and realistically it wouldn't be expected to do anything my G5 doesnt do sterlingly already.