Seriously, if I'd known at the time that Rosetta would be dropped in future OSX revisions and I'd known that the software was only PPC for Macs (I had no reason at the time to look into this) our purchasing decision would have been different. So, you could easily argue that we made an unfortunate purchasing decision, but at the same time, there was no message from Apple (that I am aware of) that Rosetta would be dropped in the future. If there is such a document/press release from Apple, someone please show it to me! I have contacted Apple, and of course had no response on this issue.
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And if Apple do not intend to do this, they should have made a PUBLIC statement 3+ years ago (when Leopard was released) that Rosetta was temporary, rather than making out that it was the best thing since sliced bread! I honestly think Rosetta is an amazing piece of software - why drop it? And why no OFFICIAL announcement about this? We are talking about a multi-billion pound company! Can they not afford to send out an email or press release to all users informing them of this plan? In advance?!?
That is why I am so annoyed at Apple. They seem to think that people only use their computers for Office/PS/iLife, which in my opinion is far from a complete depiction of their installed user base of 20-odd years.
And this is why Apple will never penetrate into corporations in any large way. Microsoft will bend over backwards to support programs that even the developer stopped supporting, while Apple will just pull the plug with no warning.
I wouldn't invest in upgrading your mac. It's old, probably has an nvidia card which means it's a ticking time bomb, and if you don't upgrade now, you'll just have to upgrade when it finally breaks, which leaves you with no time to plan for the transition.
Your two options are to either emulate OS X, or move to Windows. I know you can legally run OS X 10.7 on a virtual macine within 10.7, but I don't believe you are legally allowed to run a 10.6 or earlier virtual machine, on any mac environment.