I would be careful with the word serious, I would interpret that as a programme targeted at serious naturalists, in much the way that "British Wildlife" magazine is serious. Springwatch and Autumnwatch are aimed at a very wide audience including younger viewers, and one of it's aims is surely to educate and enthuse people of the wonders of nature. A difficult task to please all of the people all of the time. On balance, I think the three principal presenters do a good job and clearly work better together than their predecessors. I also think Nick Baker has improved presenting Unsprung.
I should also add that the programme does tackle "serious" issues to a degree, e.g.the plight of the hen harrier.
I've enjoyed the series so far, technical glitch notwithstanding. Congratulations to the BBC and ALL the presenters, thank you.