We flew into Pisa and stayed one night prior to traveling to Cinque Terre in June. The Hotel Alessandro della Spina was perfect for us. We arrived rather late, but the man at the desk was warm and friendly. He checked us in quickly, and helped direct us to a nearby cafe for a late snack.
The hotel is older (like most everything in Italy!), but perfectly clean and very, very comfortable. One of the reasons we picked this hotel was because it had air conditioning, and we were glad we had the option.
The breakfast buffet had a lot of variety, and was quite lovely and tasty. Also - if the weather is nice, you can sit outside on the very pretty patio. It is a wonderful way to start the day!
The hotel was also extremely convenient to the train station, which was helpful. Although we only stayed one night, I could easily recommend it for more than that. It was also quite a good value.
We didn't visit the leaning tower on this trip, but have been there before and its actually quite worthwhile! Definitely go to the ticket counter when you first arrive so you can get the next available ticket to walk up the tower. On busy days it can be an hour or two before a ticket is available. There are other things to see while you wait like the Baptistery, Il Duomo and a really interesting "cemetary". It is inside of an old partially restored building with some beautiful sarcophogi...our 12 year old daughter absolutely loved touring around and seeing the various images and stories portrayed on them.
All in all, Pisa is worth a short visit and this hotel is a great option while you are there.