Gideon keeps his counters (nothing in the card says otherwise), so you can just double him constantly (his P/T won't update mid-turn, though). Alternatively, you could just stick him in an EDH or modern deck with Quicksilver Elemental for a quick board-wide nuke, but that would probably get you hated on.
I wish the Simic champion had been an Ooze, but I like this one as well. It dodges Searing Spear, stops most attackers cold (including Boros Reckoner) and can provide some utility, even if he can't break planeswalkers in two. I'll be looking for three or four copies to add to my Simic-Golgari deck. I only wish Master Biomancer would go down in price anytime soon...
The wurm looks like one hell of a surprise blocker, but I don't like Selesnya as much, so I probably won't be going out of my way to trade for them.
The Rakdos creature is fun, but it looks like it will be relegated to being a dollar bin mythic since it isn't good competitively and playing it is kind of a dick move in casual.