I see no more wrong with subverting the achievement system than going onto an achievement server to unlock your new weapons. I couldn't get the cap-intel achievements, so I just opened up a tiny working CTF map I had made and got the three-times-in-a-row, without-killing-anyone, and 25-total all in under 5 minutes. What is different about 15 minutes of pressing the space bar and 2 minutes of logging onto a server and typing a command?
I understand why Valve did the achievement thing, but I find it very irritating to have to wait forever to get the things just to find out how ridiculously underpowered they are in some cases, or waiting forever just to be on par with other players. It's hard to live without the ubersaw, for instance, but the flare gun is only ever rarely really useful to me.
And people trying really hard to get that last achievement gets really old. I joined eGO shortly after a stint in 2Fort underwater as a pyro hoping I could get a few kills for the associated achievement. Hardhat ended up helping me with the last two achievements (rather than simply chastising me for using an eGO server for achievement farming). I was so impressed with the act of kindness that I joined. But I myself find it slightly irritating to uber a heavy who stops after a kill to taunt and get an achievement but utterly waste the time I took to build the uber. But he just wants his frickin sandwich, I totally understand that.
All of that said, I refuse to use a hack to get anything, it just feels low-class. I only have 2 or 3 Milestones for scout so far and it'll prolly be a while for #3 since I hate playing scout. I don't see Bonk being used all that often except when sneaking past a sentry (which actually seems to work, strangely). I can't aim the baseball for crap.. and seriously, one shot every 10+ seconds?? and rely heavily on double-jumping... the unlockables just seem to suck compared to ubersaw, sandvich, and backburner.