I could talk about this forever, but I'll restrain myself. libertymcateer makes some great points. But I wanted to add two things: 1) For most people, when I think about registering a trademark, their concern is getting priority so that other people cannot jump in and use the same mark. Registering a trademark brings a host of benefits, but you don't need to register to get priority over later users. You just need to…
Good intel. Thanks for sharing. I'm already selling my product under the name. I did do a search and nothing turned up so I don't believe anyone has trademarked anything as yet.
Honestly, given your question, just wait. If you are open to rebranding after joining YC, then I just don't see the reason to spend the money on registering a trademark. As I said, the priority issue seems to be taken care of for you. And while there are other benefits to registering, don't worry about those until you are convinced this is the name you want to use.
Good luck!