Re: Have paid off / paid off
The first suggests a more recent happening. You made some efforts and they have just recently paid off, fairly recently before saying the sentence.
The second suggests the past. You made some efforts at some point in the past, and at some later point in the past, they paid off.
I started a diet in January 2012. This morning, I weighed myself and I have lost 16 kilos. My efforts have paid off!!!
I started a diet in January 2011. By June 2012, I had lost 16 kilos. My efforts paid off but unfortunately I've gained 10 kilos back since then.
Remember - correct capitalisation, punctuation and spacing make posts much easier to read.