We have stayed already 9 times in the Sant Elena hotel and we highly recommend it. It really starts to feel as our second home, as we don't even have to mention our names anymore at the check in ;-). The staff is very helpful (also at your first stay) and friendly. Rooms are clean and comfortable and breakfast has a lot of variety (fresh fruit, eggs, bacon, cheese, lots of cakes, ...). There now also seems to be - free - wifi in the rooms (although I'm not sure if that's in all the rooms or if we were lucky that we were close to the router). We usually have dinner in the city center or in one of the 2 restaurants closeby (mainly locals, no tourists), but have now finally tried the hotel restaurant and we liked it a lot. The pasta was excellent and the main dishes were also very good. We'll certainly eat there again in the future.
The hotel is in a quiet area of Venice, so you are away of all the crowds of tourists. We always walk everywhere in Venice and almost never take a vaporetto, so the walk to the hotel from the center doesn't bother us (it's approx 20-30 minutes next to canal grande). However, if you're tired or don't like to walk too much, you can easily take the vaporetto. It is only a few stops from the hotel to San Marco. If you plan to go to the Bienale, than the hotel is perfectly located as it is next to Giardini.