I'm currently contemplating writing an OS X version of my Windows software. My Windows application still supports Windows XP, and I know that if I drop support for it now, our customers will cry bloody murder.
I'm new to OS X development, and as I learn the technology, APIs, etc., I realized that if I'm going to provide comparable level of backward compatibility (e.g. down to OS X 10.5), I would not be able to use many things that look very useful and relevant in my case (ARC, XPC communications, many others). This is quite different from Windows, in my opinion, where there are very little changed between Windows XP and Windows 7 from desktop application developer's standpoint.
So, on one hand, it seems like a complete waste to stick to 2007 or 2009-level API in 2012. On the other hand, according to NetMarketShare report and Stat Owl report Mac OS X 10.5 and 10.6 market share is still 11% and 35%-40% respectively. However, I'm not sure if these older OS users are my target audience (buyers of software utilities) if they didn't bother to upgrade their OS...
My question: Are there any other reasons I should take into account when deciding if I target 10.5 or 10.6 or 10.7 for a new application?