Cheapest way to get from Venice Airport to Hotel Danieli?

Is there a reason you wouldn't take the public bus to Piazzale Roma and then a vaporetto to the stop that is just in front of the Danieli?

No reason except I didn't know about it :) We have only carry-on bags so wouldn't be too much trouble. Is bus easy access from airport?

There are two bus lines, and they both pickup from directly in front of the airport terminal. The more expensive bus is somewhat like a long-distance motor coach, with room for luggage underneath the bus, traveling non-stop. The less expensive bus is more like a city bus - you would probably need to have your luggage with you, and the bus stops several times along the way. Both arrive at the same location on the island.

Did you check their website? There is a tab that gives detailed information on the various options.
http://www.danielihotelvenice.com/en/arrival-instructions-2

Where did you come up with €200 for a water taxi from the airport to the Danieli? Its always been €100 plus or minus for a boatload. Even the Danieli's website, for lets face it - not the cheapest hotel in Venice, says its only €110. I've never used one, that's still a bit rich for me, but if there are several of you or you have much luggage that's not too bad per person for a wonderful view and experience. Put it down to the experience rather than the transportation and its better than Disneyland.

At the airport (Marco Polo) I bought a 5E ticket from a machine for the bus ride to Piazzale Roma, the bus terminal for Venice. From there it is easy to find a ticket booth and a Vaporetto to wherever you want to go. One ride is 6.50E. Passes are available that will cover more days. There are so many people following this route, just ask or follow the crowd. My bus had a luggage compartment underneath. No problem. The vaporetto accommodates multitudes of people with luggage, strollers, wheelchairs, etc. Buses and vaporettos run frequently. You probably want Vap. 1 or 2. Don't be afraid to ask for directions. Most Venetians in the tourist areas speak and understand English.

Thanks for everyone's help! I got quoted 200E from a private guide that was recommended by a friend. Apparently this guide extends the service to "meet" us at the airport and help with directions, etc. She must take quite a bit off the top if she is now quoting 200E! I think I will stick to this website for my info instead of getting advice from a private guide!

Wow! How much does the guide quote you for a gondola ride?