The Lincoln ones are reasonably well loaded, it has actually surprised me how many are joining / leaving at Lincoln. Granted the would probably fill a 158, but this is the problem in this case changing at Newark NorthGate is not reliable.
You have a number of connections around the 10 minute Mark, For example 0906 London Kings Cross - Newark arrives 1032, change onto 1039 Newark - Lincoln and arrive 11.06. About the same time journey time as the direct train. But the mainline train arrives at 1040 and you are stuffed into a bus / taxi. People didn't like this and it happened frequently. So they drive to Newark instead (is this a good thing). The direct trains seem to have stopped the people doing this drive. Back in BR days the unit would be held, but now I have seen unit pull off before they have released the doors, but as EMR are so tightly diagramed I understand the impact 5 minutes late of Newark makes.
Are they successful - I can't comment, but they are certainly getting people off the A46. Could they do better, probably if they had decent connections at Lincoln towards Grimsby. Going the other way the failed connections didn't happen as much, but you could have some long waits at Newark for delays off trains coming from Scotland (Again Lincoln tend to start on time, but they have had 90 minutes dead time)
Sunderland and Bradford do have a very frequent local service, same scenario at Leeds or Newcastle and you don't have a minimum 1 hour wait for the next one.