I got my visa last october, and travelled in April this year.
I was very nervous about what questions customs would ask me - 'why did I have a visa' etc.
The customs official didn't bat an eyelid when he saw my visa, he just asked how long I was staying, and how much money I had on me.
I had travelled in 1993 on honeymoon, without a visa. This time with the kids I wanted to do it right.
I had to state on the form previous visits, which I did. I was not asked about not having a visa before (the offence happened in 1984). The lady asking the questions was nice as pie, and it lasted 5mins.
The reason some get visas and some not is individual circumstances.
An older guy, travelling with his family, after a D+D offence years go is not seen as any knd of risk now. A youngster, whose offence happened recently is, and he may get refused.