I bought an hb2 cp heli on ebay and it works excellent. I think that people just don't read the descriptions of the helis well enough and don't ask enough questions.

If you are buying on ebay, you have to make sure that the seller has good feedback. (96% should be almost the lowest rating that's still good) Anything below that-I wouldn't deal with the seller. Make sure that the seller is not in China or Hong-Kong or anything because they will most likely trick you. The only other country that you should buy from, should be Canada and even so, I'd stick to the US. Ask many questions if you're not sure and read their feedback. Some people leave positive feedback even if some parts are missing or shipping takes forever. Also, neutrals don't show on the percent so the seller will have 100% feedback with a bunch of neutrals and people don't look at the feedback thinking that it's perfect.

As for the corona. I think you should go with it. A friend of mine used to have one, he has since moved up to a bigger heli, and it was great and very durable.

Moe3754 is right, the sims on ebay are crap. They won't teach you a thing.

So, you decide if you want to buy from ebay or not. Personally, I've never had a problem, but that's just my experience.