The extra train each hour between Sheffield, Worksop and Retford, and the reduced journey times between Sheffield and London ought to be welcomed. However, although there will now be 2 trains each hour between Sheffield and Retford, the timings are poor, with the two trains running close together, resulting in it being far from the half hourly service that I was expecting between Worksop and Sheffield.
Taking Worksop as the example trains to Sheffield are now due to depart at xx24 and xx41 and in the other direction trains arrive in Worksop from Sheffield at xx06 and xx59. It might provide more capacity but is not really a great help in increasing the convenience of train travel when trains are timed so closely together. I can see some of the reasons why due to turn round at Sheffield and Retford, but I am sure it could be improved upon.
The trains from Nottingham arrive in Worksop at xx33 and depart at xx41 and so travel from the Mansfield area to Sheffield will be greatly improved with an 8 minute connection time at Worksop. That cuts almost 35 minutes off the current journey time. However, things are not so good when travelling from Sheffield to Mansfield as there will now be a 35 minute wait for a connection at Worksop. The journey time in that direction has not increased but the wait at Worksop has increased due to the faster journey time between Sheffield and Worksop. It's great waiting at Worksop in the mornings when the cafe is open but no fun in the late afternoons and evenings in winter when everything is closed up.