This is still and issue in 1.4.7 and in Snapshot 13w02b
In 13w02b this effects the Activator Rail and Powered Rail in the same way.
The powered rail update changes slightly depending on the power source type(torch or leaver).
Please look at the screen shot attached named 13w02b Powered Rail Bug
From left to right:
The first leaver was turned on. Then the second leaver. No power was given to the rail to the north of the second leaver.
Only when the first unpowered piece of track to the north has a block update will the track get powered.
When torches are used as the source(at the same position), the tracks are then powered.
When torches are used again, but placed at a different position it has the similar effect as the leavers.
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