Is CEX.IO a legit site?

I've been hearing a lot about CEX.IO lately, and I'm curious to know if it's a legitimate site for trading cryptocurrencies. I've done some research and it seems to have a good reputation, but I wanted to get your expert opinion. Can you tell me more about CEX.IO's security measures, the types of cryptocurrencies they support, and any potential risks or drawbacks that I should be aware of before signing up? Additionally, are there any alternative platforms that you would recommend for someone who's new to the world of cryptocurrency trading?