We have a successful payroll application developed with VFP and DBFs specifically for the laws of Panama. We feel we have a very good handle on the business problem and are looking to rewrite the application with up to date tools.

Requirements:
1. The update should be able to run in the cloud or in a customer's server and PC if customer requires it.
2. Though the main processes are normally run from a terminal in the office, the app will receive and provide data access from phones and tablets and who knows what else in the future.
3. Some of the data capture screens provide immediate feedback which requires a lot of computation, such as significant checking of historic data. Stateless web server behavior is not really acceptable.
4. The tools used should be reliable and expected to have a long life left in them. I am especially bothered by MS's habit of periodically making updates to their tools which require you make substantial changes to your code if you wish to use them. Backward compatibility of updates is something we value.
5. Developer productivity enhancing tools are a key consideration.

All suggestions and comments are welcome.

Thank you very much,

Alex