The first impression: Ahmedabad is a very dusty and very dirty city. But if you have a chance to spend there more than 2 days you will discover lots of gems - not only the mosques (Sidi Sayid, and Friday mosque) and museums (Calico Textile and city museum are the must!), but also beautiful old houses, temples, Badra fort (possible to visit now) and at least two step wells in the eastern part of old city.
Hint: as Ahmedabad is not a tourist trap at all you should know that there's only ONE place where you can buy postcards and souvenirs: boutique heritage hotel House of MG, opposite Sisi Sayid Mosque.