I find it a very usefull and reliable programm, not only you have tremendious much data, ALL over the world, it's also an online application, and yes, you need a fast mac and an even faster connection to the internet, a fast broadband I would recommend !
Once you have this two indispendable things, also usefull for all other programms, it's a very good utility and the forecasts are very reliable.
The programm has mutch evolued troughout the years, and I hope the maps will still improve on detail !
One thing could be better: when viewing cloud animation, you don't know witch image is showing up, or what's the beginning of the "movie" or the end...
I use it all over the years to plan my hollydays, and I've never had any regrets on the weather I have there !!!
So buy it quickly, you would have a wunderfull experience.
The demo isn't much, because of the limited details of the maps, but the registred copy opens a world of difference !