Well the most well known ROMs are Cyanogen Mods. But if you're new to android I would suggest you stick with Sense, because it's really simple and nice for new users... After like a year or so after getting used to android and wanting to try new stuff on your android you can try some other ROMs, that's my suggestion.
I'm sorry, but I have to disagree with just about everything in this post. Cyanogen makes 1 of many well known ROMs for the EVO, and I'm sure that will continue to be the case for the EVO 3D. I rooted my phone after just a few months of getting it simply because I wanted the "option" of having something new. There isn't anything "easier" about Sense, IMO, it's just a different UI, so things are arranged and organized differently and the options are different. Rooting really doesn't have anything to do with wanting something new as you can root and stay with the stock ROM if you choose. Rooting just gives you the option to load ROMs when you are ready for something different. That being said, I do plan on using the stock Sense 3.0 UI for a while, because it's new and I like new things. However, this will get old, for me, after a while and I will want to try other ROMs.
If you're interested in knowing, here is a list of all the more popular ROMs for the EVO:
http://evo4g.roms-db.com/
This list isn't indicative of what will be available for the E3D, but hopefully some of the bigger developer names (Cyanogen, Kushdeck, Virus, eVoKings, Misfit, Tyzing, flipzmode, aamikam, etc...) will all support ROMs for the new E3D platform.