Don't think I'd ever go and use a Mac but I'm a fan of linux (Carry a copy with me on my USB)
Nothing inherently wrong with a mac; they're really just a BSD variant with some customization added - but to each his own!
You make some good points - The learning curve seem to be very steep with arduino.
It really isn't that bad, honestly - in fact, with the Arduino IDE and libraries, a lot of very difficult stuff can become easy, quickly. Once you understand how to interface to the external hardware you're controlling (without burning anything up, and giving it the proper voltage, current, and control signals), and you understand the syntax of the language (C/C++) - it almost becomes like Lego at that point. Once you have all of that down (and the best way to learn both is to play with the examples given with the IDE, plus the various tutorials on this site and elsewhere, as well as the various beginner's books and kits), the greatest challenge is thinking about what you want to do, and coming up with a step-by-step, rational and logical plan/schema on how to translate all of that into the program code.
You won't be able to escape that part no matter what system you use. It's really the entire crux of the matter. Especially when it comes to robotics, knowing how to come up with solutions to potentially intractable problems via the combination of hardware and software is both a skill and an art, but one with rewards seldom found in other hobbies. It's long been my opinion that robotics is probably one of the most difficult, interdisciplinary studies that one can pursue, whether as an amateur or a professional researcher - the number of subjects to have a potential command of via the computer science side of things alone is staggering; add in the bio- and neurosciences, not to mention the various skills and knowledge for the mechanical components - well let's just say it can easily become an expensive but gratifying pursuit.
You'll know what I mean when you see your robot first lurch forward under your "command"...
Guess I need to way up what I want to invest - Short term toy vs long term hobby.
...or potentially - a long-term career or business, if that is something you wanted to pursue!