I, am a private individual with no job
Did you have a job in 2009 when you bought it? Spending as much on a workstation computer when you're unemployed seems irresponsible to me, but I can't claim to know everything about what's going on.
I'd meant the OP's "MacBook Server" -- OP mentioned decommissioning it and dual booting their Mac Pro into 10.4, but to me, hosting files to 68k/ppc Macs seems like one of the most monumentally huge wastes of a Mac Pro's time and electricity consumption, unless you're time-traveling to the '90s, have one of
these and a few huge disks, and are replacing a whole pile of AWS95/AWGS9150/ANS500s with the Mac Pro.
Fortunately, for the foreseeable future, I don't have any needs that can't be met by 10.4
I would probably sooner not own a computer than use 10.4 on one of my main computers. Objectively, it's fine (minus the lack of security patches since 2010 or so), but it lacks modern web browsers now (I mean, unless you really really love running a core utility like that in Rosetta) and flash is a big deal to a lot of people.
One of the reasons I often reply to people who talk about wanting G5s and Mac Pros/XServes to last forever is that despite their high cost, they're often not really designed to last a long time in a home environment, they're designed for (and are generally good at) having a normal life-cycle in a professional/datacenter environment, and then being replaced after 3-5 years. It's more of a public service announcement. (That and it's always interesting to see what people's justification was for buying so much computer.)
The problem with big computers in homes is that they become a great place to sink more and more money. (I'll be the first to tell you that my own big computer is a money pit and I would almost certainly be saving a lot of money and not losing much functionality by using something much smaller.) Often, you can sink a whole lot of money into an old big computer without ever gaining functionality. (This is more true on the Mac side of things, unfortunately, just because Apple doesn't optimize for people who are willing to spend a grand putting marginally faster processors and a boatload of ram into their old Mac Pro, rather than spending a grand on a new MacBook/air, mini, or iMac.)
It depends a lot on what you're going to do with a big machine -- Even though I could probably toss a video and sound card into it and run it as a Windows 7/8 desktop, I'm running my own big machine as a virtualization server, which means the capacity is actually used. (I'm waiting to have some expendable cash to bring it from 16 to 32 gigs of ram.) There are two issues I'm going to run into with it though:
The first is that my particular machine has eight disk bays, and I found a good deal on 2TB disks so it's crammed full of them and now I have 12TB of on-line disk capacity that needs good backups, especially since I bought and am using disks that aren't really for "enterprise" use, and may develop UREs and bad sectors quickly. A reasonably developed backup system for 12TB of disk capacity is going to cost a bomb, even if I go straight to disks (and have enough disks to hold 2-3 weeks of full backups) or eliminate the disk tier and go straight to the cheapest tape loader I can find.
The second is that eventually I'm going to either run up against the capacity of my machine, or some marginal upgrade is going to cost more than a new machine. (There are already ivy bridge corporate desktops that would probably outperform my current configuration.) It's hard to let go of several thousands of dollars of computing equipment and either make the same magnitude of investment, or acknowledge that slightly more frequent upgrades of smaller systems is easier -- both in terms of budgeting and in terms of acknowledging when it's time to be done with a system.
(Again, I know there are a lot of different circumstances, especially when Dell will sell you a machine that holds four disks and four or five PCI/PCIe slots for $399, but even on the PC side of things... those slots go unused most of the time.)
But it sounds like you knew what you were getting into and that you understand how Apple tends to do new software. And who knows, now that all vestiges of 32-bit are gone from Mountain Lion's HCL, and the oldest IGPs are gone, the system requirements may stay stable for some time.
Plus, the day after they give it away will be the day you think of the perfect use for it.
Story of my life.
).
I'm not perfect, but I'm trying to muddle through.
