We also went from a Prius to Tesla, with another electric in the stable for about 3 years:
My wife drive a 2007 Prius to 170k miles before we got her Model S this year
I have a Roadster with 70k miles
My older kids both drove a 2009 Zenn (think "refined" Zap with 4 wheels) during high school
A fellow I knew had a Zenn. It was a better car than my Xebra in every respect except one: The Zenn was a good solid boring NEV. The Xebra was fun. (I'd have kept it if it hadn't been so dreadfully under-powered.)
... every day that the Model 3 isn't ready to be test driven or sold is a day that the reservation holders will, in many cases, decide to go with an alternative.
If and when there are delays (which I think is quite possible) this may be the case. But at present the Model 3 seems to be still on track. Everyone who placed a reservation knew, or should have known, that production would not start until late this year, and unless you are an early reservation holder you probably won't get the car until 2018. Anyone who cancels right now because they're tired of waiting probably wasn't all that interested in the first place because it's not scheduled to be ready for nearly a year. And nobody has cars to test drive a year before they're available for sale. Some people will just change their minds. But it's worthy of ridicule if someone cancels just because they think the news of the contract cancelation means a significant delay in production.