It is not a very pleasant city in general,there is a lot of traffic and the weather is generally grey especially in the garua season ( April to November) Unless you have friends there, I would not recommend spending more than 2 days in Lima. You dit not come to Peru to see Lima anyways
Favourite spots:
Miraflores is the place to hang out at night and old lima is certainly worth spending a couple of hours.
What's really great:
It is nice to hang out in Miraflores overlooking the pacific ocean
Accommodations:
Lima is a very big city, you should be staying in Miraflores, do not stay in Lima centro, there is nothing to do at night and it looks a bit dangerous. We stayed in San Isidro (near Miraflores) at the boutique hotel Suites el Bosque on Paz Soldan (corner of Arequipa near Miraflores). It's 5 star for USD 50(including a nice breakfast). It does not get better for the price. It is more a business hotel, so do not expect to meet other travelers.
Restaurants:
Brujas de Cachiche in Miraflores, very nice peruvian food, must try the ceviche.
Expensive but worth the splurge.
Bolognesi