ice is cool
seriously though, ice is great for role-playing purposes as well as for the stated fact they are rarely picked (though as it seems this is soon to change).
Another point is that ice planets are commonly spread on the outer part of the system. this means a much better chair of protection. debatable advantage though.
one (two) Last thing is that ice planets seem to have better organic values and worse mineral values. also ice planets seem to contain ruins more often that other types.
on the cons though they seem to be usually of the smaller sizes.
overall i believe its a well-balanced type of a planet. it might give you disadvantages during early game but its all luck and chance - often enough i get ice/[breathable] planets in my homesystem. sometimes i dont. some systems only have ice planets, others have none at all. and so on.