In reply to Jonny Tee 69:
I have a normal Alpkit one and one of the tiny ones for wild camping. The tiny one needs repairing (I thought it had developed a fault, until investigation revealed a large gash in it - gaffa tape will sort that) but the large one has been fine for a couple of years now. And Alpkit have great customer service / repairs / refunds etc.
I used to just use a foam mat, and comfort wasn't really a problem (when I started bivvying out, I didn't have a mat at all, so anything was a bonus!) but warmth was. I sleep very cold, and after a few unhappy winter nights waking up shivering, I thought the extra insulation of an inflatable mat may help, and it did. Never have a problem sleeping through the night in the cold anymore.