Israel's tactical victory in Operation Pillar of Defense is fairly straightforward: Hamas's military infrastructure is significantly degraded, several important leaders of Hamas (as well as Palestinian Islamic Jihad) have been killed, and the Iron Dome missile defense system has proven extremely effective. If the ceasefire announced today in Cairo holds, it's also a major strategic victory for both Israeli and American interests.
Read Lee Smith's excellent analysis of the regional implications; written before the ceasefire announcement, it details how successful US diplomacy could force Egyptian President Mohamed Morsi into the role of containing rather than supporting Hamas while simultaneously sending a strong message to Iran about Israel's ability to act unilaterally with US support. While things could fall apart, the announcement of a ceasefire that is basically on Israeli terms -- though the deal may include some easing of the blockade of Gaza, it apparently does not include lifting the blockade as Hamas had been demanding -- suggests that this diplomatic success has come to pass.
UPDATE: News from Israel at the moment -- 3:00 pm EST, 10:00 pm in Israel -- is that despite the announcement of a ceasefire beginning at 9:00 pm, the fire hasn't actually ceased. Take the above analysis as contingent on that happening, obviously.