Our Opinion

Pisa is a small, compact city which is easy to travel around and relatively safe. You can probably see all the major sights in a single day but two would probably be better. For much of our stay we experienced torrential rain (this trip was officially re-named The Brolly Boys - see picture above!!) but this did not stop us getting about and seeing the sights
The main tourist attraction is obviously the Leaning Tower but there is plenty more to see and do.
Pisa is, however, a rabbit-warren of courtyards linked by small streets and alleys and a map is essential. The local tourist information office (located in the main square close to the railway station) is a good place to start your visit.
We experienced both good and not so good food in Pisa, in general, our advice would be that the further away you get from the main tourist attractions, the better standard of food and service you are likely to get. On our first night we had a splendid meal in the old town but on the second night we ate around the corner from the Leaning Tower where the quality of food was much lower and the standard of service left a lot to be desired.
As with much of Italy, Pisa is not full of bars although most cafes serve beer. At night, restaurants tend to be the place to drink. Beer is not that cheap but we found the local wine to be both palatable and inexpensive.

Further Details

Travel
Liverpool - Pisa with Ryanair
A typical Ryanair flight where no frills equates to almost complete lack of service (although since this trip, one of our number has actually experienced total lack of service from them). The final insult was being sold plastic pouches of low quality gin at a high price. We will not be flying Ryanair again.
Pisa - Florence with Italian Railways
A fast, reliable and (by Italian Railway standards) punctual journey. Note, however, that this is a very popular route and the trains tend to get very busy and crowded.
Local buses
There is an extensive bus network in Pisa although many services only run during the day time. There is also a good bus service from the airport into the city centre. Take care, because of the small streets and compact layout of central Pisa, once buses get into the city centre they do not always take the same road (or indeed even adjacent roads) in both directions. A local map is extremely handy.

Accommodation
Grand Hotel Duomo, Pisa
A good hotel, and given its proximity to the Leaning Tower, remarkably inexpensive.
The hotel has a bar and a restaurant although we didn't eat in the hotel. The bar is well stocked with a friendly barman together with a somewhat strange collection of British football memorabilia.
The hotel is situated about 100 yards from the Leaning Tower and around 1 mile from the city centre. There is, however, a reasonably frequent bus service from nearby to the city centre.