It seems that Saintvicious never purchases Wriggle's anymore—he always goes double Doran's => Vampiric Scepter => Frozen Mallet or Blood Thirster.
It depends greatly on the champion. Characters with strong AoE clears like Udyr and Mundo, don't need wriggle in order to maintain their jungling speeds.
It's a heavy early investment, but a it's for good reason. It helps you maintain jungle control, speeds up dragon/baron, gives you all the things you need to jungle effectively.
If you comment and tell me which junglers you like, I can tell you whether it's worth continuing to buy wriggles.
Its called vampiric scepter, it give a huge advantage, but i think they only get it if they are in the lead, a lot of junglers like Shyvana and Lee still get it, it gives a ward, ward = vision, vision = win, and that's 75g per 3 min, so its a great item :)