I love Lidl. We've been on an economy drive for the last year so I started going to Lidl and now I go most weeks. Particular favourites are:
Maple cured bacon - Sainsburys used to sell this and we loved it, then they stopped - I was ridiculously happy to find it in Lidl
Vast refill bags of Cien hand soap - I love the milk and honey one
All the copycat chocs are great, fake Snickers etc
Pasta sauce - we use the onion & garlic one on our pizzas, it's yummy
Tinned sweetcorn - no added salt or sugar, unlike most of Sainsburys varieties
Artichoke hearts in oil - love these on my pizza 
We regularly buy Lidl fruit, veg, part-baked petit pains (so cheap!), milk, butter, cheese, fruit juice, flour, pasta, ketchup, soy sauce, eggs.
I've never had problems with the fruit and veg going off, it's all equal to Sainsburys quality in my experience, and the meat is equally good.
I'm a total convert. I like their special promotions too, you never know what new things are going to be on the shelves. I bought some terrific snow boots for the kids last year.
There's an Aldi opening near us in a few months and I'm looking forward to trying it for comparison 