Startup Revolution

I agree with all three of those reasons and would add these 7 ideas about why you can no longer afford to ignore GooglePlus:

• Google Plus is NOT a social net per se, it is a "revolution in online communication" and a "tool" says B. L. Ochman. 
• If you don't figure out how to use this new tool your competitor is sure to do so and then PAIN will result.
• Other social nets are becoming endless tit for tat smackdowns (you gain 1,000 followers they gain 5,000) so why play that losing game when GPlus is almost always a blue ocean?
• No better conversation tool than GPlus (period) and this time is all about the social conversation.
• No one has millions of followers yet on GooglePlus (or very few do) so your chances of being followed back are excellent AND GooglePlus promotes conversations not just follows.
• Since GooglePlus is a TOOL it is invested in making YOU the publisher successful not requiring you to make it successful like most social nets.
• Its's Google.

One final thought. I've lived through several major tipping points such as the move to commerce from brochureware, the mobile revolution and the social revolution RIGHT NOW feels like the GPlus Tipping point.