There is a difference between akruti, shree lipi and aksharmala (itrans). Bot have their advantages and disadvantages.
Aksharamala text is searchable and can be uploaded on net and can be viewed on cross platform, if the system has indic language support. Only a indic unicode font is needed g.e. Arial Unicode MS. Search robots can identify and index unicode and itrans text and can show them in the search result.
Akruti has wide range of fonts to select, good for creative work and making art cover, banner, etc. But typing scheme (keyboard layout) is different from unicode.
Ubuntu Linux has asian language support and has indic language pack. there is an app called as ibus, through which you can select any language. After enabling the language, who can directly start typing in that language. Keyboard shortcuts are also available to switch between languages. In some languages, more than one keymaps are available. e.g. in gujarati language, i can type using itrans keymap, inscript and phonetic. Text will be in unicode, and searchable.
I dont know if similar app is available in iMac. In opera browser forums, there is a thread regarding rendering of east asian characters (japanese), the questioner was using mac and he said that the east asian language support is inbuilt in Mac, so no need to manually enable it through 'regional and language settings', as in case of windows XP.
All you need is a Indic unicode font and an app (inbuilt or 3rd party app like aksharamala).
Since I do not have Mac, I cannot help you anymore.
Regards
Sujal