I'm by no means an expert on the topic of integrated PhDs and so I'm asking if anybody has any opinions concerning integrated PhDs. Are they successsful and rewarding?

Obviously integrated PhD are much better for those who are determined enough to continue their work in same field. Since the view is more focused hence more beneficial.

what's an integrated PhD?

An 'integrated' PhD is a new type of UK PhD which follows a 4 year programme and involves a significant taught element alongside the research project.