We have stayed at the Bonanno several times, either at the beginning or the end of holidays in Tuscany, as it is so near Pisa airport. It is quite a large and impersonal hotel and, whilst I wouldn't wish to stay here for any length of time, it is fine for a night or two. The rooms we have stayed in have always been clean and are a decent size. Similarly, the staff we've encountered have always been professional and the reception staff speak fluent English. The hotel serves an extensive hot and cold breakfast. Some reviewers have mentioned the location and although it is correct that the hotel is on a roadside and you need to walk through an underpass to get into town, this has never been a problem for us and we have never been disturbed by traffic (or any other) noise. The hotel is located in a fairly middle class area and the underpass is lit and is safe.

The Bonnano is a short walk away from the Leaning Tower. Whilst this is well worth seeing, the area immediately around the Piazza dei Miracoli is overrun with market/street traders selling tacky wares. This area also has an abundance of awful restaurants vying for the tourist trade. Walk further towards the town, however, and you will find plenty of decent places to eat.

My boyfriend and I stayed at Grand Hotel Bonanno for 2 weeks in October 2011. Could not fault the hotel or staff who were always helpful. The location of the hotel is excellent for train stations 5 min walk to San Rossaro and 20mins to Central or 5 mins on a bus. The breakfast was very good with plenty choice, we only ate twice in the resturant in the evening and it was also very good. Excellent Pizza resturant 5 mins walk away called Pisakech.
Would recommend and would definately stay again

Everything very good including thé price being a 4*. Only neg comment are thé rooms a bit small. Staff is fantastic and makes you feel at home. We ate dinner also and were pleasantly surprised as thé restaurant isn't thé busiest. I know where to stay now in pisa

The hotel Bonanno is a good choice of hotel if you must visit Pisa.
Why? because it is a few minutes' walk from Pisa railway station (opposite the hotel, walk under the underpass and continue down to the river, then cross the bridge to reach the station). It is also a short and inexpensive taxi ride from the airport if you can get a cab as there are very few and the wait is long especially late at night which is the only time when it is worth taking a taxi rather than using the train.
The hotel is modern. It is located ina residential district, and you can walk to the Duomo and the Leaning Tower quickly and easily. Right by a busy main road and adjacent to the railway line, the hotel is not pretty, but it is clean and adequate.
But why would you want to stay in Pisa? Surely only when you arrive on a late flight and have no time to travel to Florence. There's not much to do when you have seen all the buildings around the Duomo, and you can do that with a multiple ticket in a full day.
Best to stay in Florence (and hope there is not one of those Italian strikes that stop the trains unexpectedly for a whole day).