Microsoft is constantly working to improve the Windows Phone Marketplace experience. A few months ago we saw a commitment to the quality of apps appearing on the Marketplace. Now Microsoft is turning its attention towards the turn around time it takes an app to go from submission to appearing on the Marketplace.
It now takes three to four business days, roughly speaking, for an app to go through the certification process and be published on the Marketplace. The lag time between certification and having an app available is now about one day.
For example, recent updates for Logoarama and People Search took about four days with the updates becoming available under 24 hours of certification.We are still seeing it take about 48 hours (or longer) to have price changes become visible but the overall app submission process seems to be improving.
Source: Windows Team Blog