Yeah, when you have a jackrabbit start against a creatureless deck and you can use this to get your guys back, its pretty good, but against a good chunk of the format, it either does nothing (no enters the battlefield ability) or helps your opponent out as well by giving them back a ton of good utility creatures
I cant really give an objective evaluation of how good they are, since the main purpose of Planes is be fun, but we can take a quick look at them: Tezzerets home shard on the plane of Alara, and the most metal place in the multiverse outside of New Phyrexia itself
With an unheard of 2 toughness, and prowess, and haste, for a single red mana, at common
New Phyrexia Blade Splicer Maul Splicer Wing Splicer The Splicers are an unnamed mechanic that showed up on six cards
Anything that I missed
I'll look at the themes, strengths and weaknesses, and the commanders to help judge this