I have used the DocuSign module in a customer project. It's a B2B application, where customers of my customer sign quotations in the range of €10k to €60k. My customer accepts electronically signed documents as legally binding. I think that is your biggest obstacle to overcome, to have the deliverer of the goods or service accept the digitally signed document. Customers of the customer don't seem to have a problem with electronic signing.
On a more personal note, one of my friends is board member of an association that maintains an appartment building (rather common in the Netherlands). He's often asked to sign quotations by printing a PDF file, signing it, scanning it and sending it back. He scanned his signature and pastes the signature in the PDF file, simply by using Adobe Reader. To day, he's had no party complain about this method. Compared to this method, DocuSign is a more secure alternative.