The construction on I-35 is not major, but can be constricting. Some folks can't stand it, some folks have no problem.
281 is a valid alternative though I wouldn't drive the extra mileage.
The only 'issue' with 281 is a relative lack of truck stops and gas stations with room to get a long MH or trailer into.
But it is a less stressful drive than I-35.
I don't like the congestion in Temple or in Austin - but its not bad enough to go around.
You just do not want to cross Fort Worth or Austin anywhere close to rush hour.