It also applies to Planeswalkers, so you can use Jace, Architect of Thought's ability then play another Jace, AoT or upgrade to Jace the Mind Sculptor and remove the old Jace.
There's a bit of speculation that this Legend/Planeswalker rule change is due to Theros block having a lot of legends a la Kamigawa. From a flavor standpoint it feels odd and Phantasmal Image weeps silently, but I think players will get used to it.
I also have no problem with the "number of land plays" rule.
Basically, if you had something Exploration that allowed you to play an extra land each turn, you could use Exploration's land drop, bounce it, and recast it. That allowed you to use Exploration's land drop all over again. Now Exploration basically reads; +1 land drop allowed. You played a land? That's 1 land play. Exploration gives you a second and you use that, then bounce Exploration and recast it. The game knows that you're only allowed to make two land plays - one for the turn and one due to Exploration. It sees you played two, so you can't make another.
-For constructed tournaments sideboards no longer have to be 0 or 15 cards, they can be anywhere from 0 up to
15. Also, sideboarding is no longer a 1-for-1 affair. You may bring in 5 and take out 1 or vice versa as long as your main deck stays above 60 and your sideboard doesn't exceed 15. This prevents a lot of those 61-card decks after sideboard that were game losses.
-Indestructible will now be an actual keyword instead of "just a characteristic." This matters because
Case 1: A permanent is made indestructible by another spell or ability (for example, Withstand Death), and then it loses all abilities. Previously, it would still be indestructible, because that was just something true about the permanent. It wasn't an ability the permanent had. With the change, the permanent will no longer have indestructible.
Case 2: Creatures (or permanents) you control are made indestructible until end of turn by a spell or ability (for example, Boros Charm). Previously, a creature that came under your control after that spell or ability resolved would be indestructible, as that spell or ability didn't change the characteristics of any creature. With the change, that new creature won't have indestructible as it wasn't under your control at the right time to gain it.
Pulled my first Tarmogoyf ever. Or rather my son did. I bought a lottery ticket (aka a booster of Modern Masters) and let him pick out the pack since it was his birthday and maybe he'd be lucky. Oh boy was he.