Nice is stunning, you can easily spend a few days walking around the city. The old town has a nice charm to it in the evening. We found a few good places to eat there, not sure there are many bad places to be honest,
some over priced but then its a tourist destination so you sort of expect that. We werent being cheap but had big lunches and it was really hot so didnt eat that much. The restaurants on the Promenade Anglais are a bit pricey but the beach side terraces are quite nice for a posh night out!. We had breakfast out most mornings just soaking up the atmosphere and enjoying the nice relaxed start to the day, 5-7 euros will get you a few pastries and a coffee from pretty much anywhere. Everyone seems to buy an ice cream or waffles and wander round on warm summer evenings.
The Promendade des Anglais is miles long and just hugs the coastline so you can walk for ages back towards the airport and the view doesnt change! When we were there they were rebuilding the Promenade du Pallion but I think its finished now and should look nice.
Arm yourself with a map and the walk over to Villefranche is worthwhile too, another beautiful little town. Get the train/bus back!
Get the train to Monaco too and just wander round, its a fascinating place and well worth the trip. There are a few pavement cafes overlooking Plage Neptune which are surprisingly cheap btw. Then just walk around the grand prix track and make car noises when you see some red and white kerbing. Wander round the harbour too and pick a yacht. There isnt that much in Monte Carlo at all, its basically the casino and the bank but a day in Monaco is an experience. Wealth like you just wouldnt believe. I like cars a lot but I got bored when I saw the seventh Lamborari in the first ten minutes of being there
A day in Antibes or Cannes is nice too, lovely scenic train journeys hugging the coast and some nice bits in each.