A 2/2 for two mana is decent in both blue and black, so that's a good start. This guy's abilities would be awesome if they did not have that "play only as a sorcery" clause, but they are still relevant in some games. What's good about this guildmage is that early on, it's a 2/2 beatstick, and later on it's a card drawing engine that must be removed. The abilities are a bit overpriced, though, to be playable in any game that's swinging fast.
My rating: 6/10
Two very useful abilities, reasonably costed. Countering activated abilities is not usually worth 3 mana, but sometimes it saves you by locking down a Visara the Dreadful, slowing down a Meloku the Clouded Mirror or just nullifying Legacy's Allure, Squirrel Nest and a variety of cards including planeswalkers. It's mana intensive, yes, but frequently relevant. Tapping creatures for 3 mana is even better - it will typically nullify fatties that could hurt you the same way good old Icy Manipulator does, but it will sometimes be useful for tapping key defenders.
My rating: 10/10
Neither of its two colors are strong with creatures, so him being a 2/2 for 2 is good already. The first ability makes every card in your hand an overpriced Disfigure, which is not much, but may come in handy to kill pesky elves when the rest of your removal has been spent. The second ability, though, is more useful and although it's expensive, works good both in attack and defense, making micro Ball Lightnings or chump blockers.
My rating: 7/10
A popular aggressive combination that can definitely use a 2/2 for two. His abilities are too expensive to use in aggressive decks most of the time, but he can be used in the late game to deliver those extra points of damage.
My rating: 4/10
Both green and white are used to 2 mana 2/2s with good abilities, so this guy's power had to be good, and they are. Creating saprolings can break stalemates and get you a significant advantage as well as create one, if you're being beaten. It has synergy with the other ability, which works wonders on weenie decks, creating complicated blocking conundrums for your opponent.
My rating: 9/10
His abilities seem overpriced, and they are. However, repeatable is the keyword here. At the beginning of a game, it's unlikely any of those will be activated unless you aren't using your mana well. Towards the end, however, you'll be able to activate them twice or three times a turn, draining life quickly from your opponent if you're the beatdown or gaining life if you need more time. A mediocre guildmage early on (that is, if a 2/2 can be mediocre early on), but one that takes games when they drag for too long.
My rating: 7/10
Red and blue are not used to having Grizzly Bears so this one starts well. Its abilities, though, are very situational. They sound very cool to abuse, but the restrictions imposed make them very rarely useful. It can't be used to copy an opponent's spell, so it doesn't add to defense. The restriction that the ability has to have a CMC not higher than 2 means only a handful of the available spells in your cube are copiable. Maybe someone will make a deck that breaks this guildmage, but besides the very occasional double Lightning Bolt, he has been disappointing.
My rating: 3/10
When he was released, damage went to the stack, so a creature that was on its way to the graveyard anyway could be sacrificed. Now this trick only works with blockers, and they won't deal damage, so it has been nerfed. Still, this could be useful in certain situations, especially when using token makers or weak/recursive creatures, or when you need your dead finishers. The second ability is extremely slow, although when mana flooded, it can't hurt.
My rating: 4/10
Since white and red frequently result in a beatdown deck, this guildmage is first an efficient bear, which can make combat quite difficulty for the opponent by imbueing your creatures with first strike at instant speed. Also his haste ability may seems very threatening, if the opponent is already low at life. A guildmage with situational abilities, but the right ones for those colors.
My rating: 6/10
A bag of tricks in itself, despite being situational tricks. In decks with +1/+1 counter producers, this guy is awesome, providing as many combat tricks as your mana allows. The aura ability seems like a version of the +1/+1 ability at first glance (not that moving Boar Umbra around is bad), but it's also a great defense against Pacifism-like stuff. Getting back your Confiscated permanent by moving the enchantment to an opponent's land feel awesome too.
My rating: 8/10