I think it depends who you ask. For me, someone fairly new to cryptocurrency, I think using a credit card to buy bitcoin is ok because it gets my foot in the door. I don't expect to get rich learning this technology but I don't want to miss the chance to try. Will I lose money, probably but I always get a chance to earn as well. I bought bitcoin, last september and ethereum about a month ago as well as some litecoin and so far I'm happy with my choices.

For EOS, I'm going to wait and see what things look like before I buy into it. I've started to setup a server for testing the code and will try to only buy once I've decided the code is where I need it before I should invest.