If you are talking about the causeway over Bayou Teche, its as rough as it ever was (I last crossed it 2012) and there is not anything they can do to eliminate joints for the bridge sections. I just settle into a speed where it jars me the least.
US-90 remains available as a longer, slower, low speed alternative between Lafayette and New Orleans.
I generally try to plan my trips to the southeast so that I don't go through Louisiana at all (some other major highways are also sub-par), coming from I-10 in Texas, Louisiana is difficult to avoid.
Tom Test
Itasca Spirit 29B