Greenlight was a great feature as an aditional service to get games on Steam.
As the sole way for indie developers to get on Steam it's an extremely lacking service, and this is a very short sighted move. No longer is getting into Steam a matter of quality (some would argue it never was, with some truth), but a matter of popularity and promotion ability, which skews things to games with higher budget. It essencially blocks the smaller good/great titles from getting into Steam, which was the entire point of the service in the first place.
This wouldn't be bad as long as the people responsible for selecting games to be sold on Steam (before Greenlight existed) still manually pick titles off the service, effectively replacing contacts made by emails for the greenlight pages. Unfortunately so far it seems that all they are doing is allowing the most popular games into the service, which is a really bad policy, especially when you have cases of publishers with enough pull doing sketchy moves such as "We'll give a free game to everyone that votes for us" such as Postal 2.