They are doing a major rebuild or I-35W on the north side of Ft Worth. But it covers only a few miles.
There is also a lot of rebuild going on north and south of the Temple area. But they generally do a good job of keeping traffic moving thru that area. Been thru it 4 times since sept and traffic flowing at or above posted limits.
Many people go west to US 281 before they get to Ft Worth and take it all the way to San Antonio. But that means lots of small towns, traffic lights, and lower speed limits. Takes longer than I-35, but more scenic. I prefer to just grin and bear it for those few miles of construction and get on down the road. Mid day makes it easier.
Really just a matter of what you prefer.