What kind of forms does your application cater for? pdf?
Are the forms display only or read/write?
What kind of spreadsheets does your application cater for? excel?
How sophisticated are the spreadsheets? Do they use formulas/totals/etc?
Are the spreadsheets display only or read/write?
What are the other potential target platforms than windows?
Is distribution and installation of an application an issue?
You mention moving to another technology to gain more flexibility - what kind of flexibility do you desire?