(we're off-topic now, but it's interesting anyway)
10.4, unless I have it wrong, had one "feature" foreshadowing the future: they removed the possibility to set the region parameters independently. I.e. you could only choose a region, and then you got the lot of that region. For example, if you chose anything that included English, you had to live with the comma as thousands separator. If you chose Switzerland you could not set the date format to YYYY-MM-DD, it had to by DD-MM-YY.
This caused discomfort to me for about two years, during which I had to carry the system preferences pane over from the previous version, overwriting parts of the official one, so that I could at least get what I needed. Fortunately later versions re-introduced the parameter independence.
I'm one of these "internationals": I use English all the time, but my currency is the Euro, I do everything in metric, my date/time format is ISO (YYYY-MM-DD and 24h clock) and to avoid all confusion between French, English and other number formats, I prefer the Swiss separator for thousands, which is the single quote (').
10.4, for all its other qualities, did not allow me to get that combination of parameters.
Obviously if you have spreadsheets etc., you don't want the operating system's inflexibilities to louse them up automatically at each update…
But the problem went away with Leopard.
Similar problems occur with certain apps: they just cannot imagine that one may want something more sophisticated than the "standard package".
I'm still treated badly by many websites: they detect that my IP number is in France and then insist on presenting their pages in French.
Living internationally is difficult: my phone often starts roaming because the signal from a nearby Swiss mast is stronger than that from the local, but further away French mast and conversely I sometimes stick onto the French GSM while in the middle of Geneva because its signal happens to be better. Sigh again.
