I have been playing a Lythic (humanoid-ish Earth elemental) that has earthglide (a method of movement through the ground that is similar to flying) as a PC. With the blessings of my GM. I'm finding that it feels really overpowered. This campaign is underground-bound only, so I can constantly be hiding/traveling through the ground to avoid all sorts of things. Flight is one thing, but earthglide is literally doubling as a way for me to hide while I don't want to be in the combat. Slipping under the ground without a problem, and then popping back up where the bad guys are (Tremorsense 100').. Well, it just feels like it's pushing the bounds of any kind of balance.
Despite being the player of this character, I can't help but feel mildly sorry for the GM (whom is probably a little irritated at having to deal with all the wild possibilities from my being able to essentially go off and do whatever with near-impunity).
I'm curious how other people would deal with this in their games? Would you just go with it, and figure out how to deal with the character as it's overpowered? Try to find limits of earthglide (it is rather slow afterall)?