When he was first released in Lorwyn, initial reactions were mixed. The conflict between keeping Jace out of burn range with his +2 ability while also gaining some card advantage (and thus NOT giving your opponent a card) had players wondering what exactly the correct play should be.
Now, after two years in Standard, the question is still likely to get different answers.
While there are going to be cases where the opposite is true (namely when playing against a deck with few creatures and no burn), my usual strategy for playing Jace is to use his +2 ability immediately, putting him at 5 loyalty. This keeps him out of range of the most common burn spells and relatively safe from most creatures. If my opponent wants to commit an entire turn to attacking Jace, or wants to use two burn spells to take him out, then I’m fine with that. More often than not, though, putting Jace up to 5 loyalty allows me to get at least another card out of him, and even at 4 loyalty he’s not easily dealt with.
At this point, although this is dependent upon the state of the board and my opponent’s hand at the time, I’ll usually just draw cards off Jace until he’s at 1 loyalty. If I have another Jace to play, I’ll draw that last counter and play a new Jace; otherwise I might put him back up to 3 counters and give my opponent a second card. By this point, however, I’ll have drawn six cards from Jace to my opponent’s two! As you can tell, things can really get out of hand if Jace is left alone.
At his worst, with this strategy Jace breaks even, replacing himself and causing your opponent to either use their extra card to remove Jace or use their attack for the turn to get rid of him (essentially gaining you 5+ life). Anything beyond that is extra, which is what makes Jace such a strong card (and I feel he’s still underrated).