Strangely enough, last week I was just talking about UC to another DWP escapee. We were talking about the main benefits being merged into UC all being 'gateway' benefits and how on earth was the IT system going to cope. The answer is it doesn't. Like every other similar change, the development of the UC IT system has been a disaster from the start - and the reason why UC is so far behind schedule. The benefits system is still far too complicated.
Trouble is I don't think the information mentioned in dj's link is all correct. UC is a working age benefit, so the 'unclaimed benefits' data should not include pensions information. Also, some high value additions (premiums) will be cut as part of the transfer process. Remember that the maximum amount of benefit payable is being reduced too. I think the writer makes a good point, but it is not as straightforward as he makes out.