Well, I am rude on BTC itself, not on any person who uses it for something. As I have mentioned, I have myself made lots of money out of it. But still, this does not mean that someone else will get rich in the same way as I did. I was just lucky, and that's it. So, I won't put my money in BTC again, because I don't believe it will reach 1M USD as someone thinks about.

However, the problems I am worried about are already mentioned by me in this topic. However, I will still list them out:
1. Wallet creation and sync takes too much time. In other words, if you want to participate in this network, you have to wait lots of time.
2. Encryption is not quantum-proof. This means that bitcoin has no way to protect itself against quantum attacks. However, there are already cryptographical principles which allow to do so, and they are mathematically proven as correct ones.
3. No regulation in law of any important country. I.e. let's take gold. Every country in the world tries to have more and more gold which shows that gold is at least a way to save your money from inflation. And BTC? No one serious recognizes it in law still. So, you can't know if BTC will be forbidden by US tomorrow or not. In other words, there are still too much unknown, and it is strange that so many people believe in BTC. Out of this belief, I was able to get rich a bit myself. For that I am very grateful. But also I am worried that these nice people will lose their money eventually. ANd lots of money.