I've got GAP insurance, but since my car was bought outright I've probably taken a slightly different product to you - I didn't have to worry about paying off the loan if my car is a total loss, so my insurance was more to avoid me taking the full depreciation hit if I wrote it off in the first few years (since the first 3-4 years of ownership have the biggest depreciation, and I'm intending to keep my car for 6-7, which spreads it out)
I went for a vehicle replacement scheme, whereby I don't just get the invoice amount, I get the cost of an equivalent specification car. I figured this makes sense if, like me, you get a decent discount (I got something like 15%) because it's an out-going model, and the next model is more expensive. A new model A3 with the same spec as mine would cost several thousand more, and when the new model came out discounts were nowhere to be seen.