Pretty much all the estimators I know still rely on their Excel spreadsheets and don't have much use even for estimating software let alone cloud based solutions. Estimating is a very conservative discipline since a contractor's viability as a business rests on the reliability of the estimates and they stick with what they know, trust, and control.That said, there is a cloud based program which I have recommended to some estimators with very positive responses. The service is called Assemble. It works by publishing Revit models to the  server which can then be viewed and analyzed by their viewer. The beauty of it is the ability to visualize the building components alongside the estimates, quantities, and such. It also retains the information from each iteration of the building model and can compare them to show what has been moved, added, deleted, and/or changed with each update of the model. Even without the estimating part this feature is huge. Of course it is not a replacement for traditional estimating as it depends on the accuracy of the model which is created by someone else so the estimator won't fully trust the results (at least not to start with). What it does provide is a terrific reality check and alternate view of the estimate that can greatly assist the estimator to check, refine, and document their work. For more info you can check it out at: Assemble Systems | BIM Construction Software