We have just returned from a lovely 75th birthday long weekend at the Corte Grimani. Perfectly located between St Mark's Square and the Rialto Bridge. 3 of us stayed in a corner canal-view apartment that could have accommodated 6. Lovely spot - being serenaded by Gondoliers as we sat and drank our cocktails in the evenings! Very clean and bright plus very helpful staff. They provided free wi-fi password for the stay, umbrella when it rained, printer for tickets, advice etc. etc. Lovely pastry shop nearby for delicous breakfasts.
We walked there from Bus station on arrival - DON'T DO IT! (wheelie cases don't mix with steps on bridges and it takes 45 minutes) - use Vaporetti to Rialto instead - efficient and frequent.
Will definitely be back.