I have not read all the comments since there are too many of them. Here is my wish list(I am an ex- Mgmt consultant) without knowing if its already covered in the comments:
1) Creating a new tab/sheet and choosing if the tab should be a document or spreadsheet type so that I can run my numbers once and reference my table in the document and not worry about cutting and pasting. Really helps reduce word document and report writing. This is a fundamential mind set shift as an excel spreadsheet hardly goes on its own. Its always accompanied by a document and syncing the numbers between the report/tables and the excel is a massive PITA.
2) Importing some functionality of Access (running unique/group by queries, inner join/outer join etc...) in Excel. Helps me run complex data queries while maintaining data integrity.
3) A wiki like online spreadsheet. (dont think Google Docs does this. For e.g. if we are running a valuation for a company and each team mate has different assumptions for each variables, this can help team mates input thier assumptions and track it and see the overall impact on the numbers. Instead of the current model of emailing spreadsheets back and forth or erasing new data over old ones (e.g. like Google Spreadsheets). Btw- I strongly believe just implementing this last point alone and narrowly defining yourself as a model builder (with wiki like enterprise capabilites) would generate strong traction in I-Banks, Buy side firms, sell side research firms, market research companies, mgmt consulting firms, insurance companies etc...
Would love to try out a beta version if available. my email is raonikhilesh "@" gmail