My background is in VUI design, and one of the very first things I ever learned to do is "escalated error handling."  This means that, in addition to an error prefix like "sorry" or "I didn't catch that," the actual wording of the prompt is changed to give callers a better chance at answering it the second (or third) time through.  Sometimes this means giving more detail about what's being requested, such as the specific number of digits in an account number, or the exact keywords the grammar is expecting.  Sometimes this means adding more information to help callers make a decision, such as by giving a few examples of what data is included in account information.  Always, this means designers of speech systems recognize that it's usually the fault of the system when callers fail to respond...and they try to adapt.

Strangely, this best practice isn't very prevalent in the DTMF design world -- even though the practice has little to do with the input modality.  The vast majority of touch-tone systems I call simply repeat the same prompt over and over until I get kicked out of the system (and sent to an agent if I'm lucky).  Now and then I'll get an unhelpful, robotic prefix like "that response was invalid," and occasionally there's at least an acknowledgement of the repeat with a simple "again." 

My conclusion is that producers of DTMF applications, perhaps feeling second-fiddle to the more complex speech options available, don't tend to give their systems the attention they require.  Or is it that the companies who offer DTMF applications don't hire the right kind of designers?  Just because speech technology demands a high degree of end-user focus, that doesn't mean touch-tone designs can skip it.  The same people are calling both kinds of applications.  The same people have complex goals, regardless of what telephone technology their banks and airlines and insurance providers offer.  The same people need to be reminded how many digits are in their account number.  The same people might need to know what exactly is meant by "account information."  

The good news:  There is a lot of room for DTMF systems to improve.  Escalated error handling is just one example of how so many touch-tone systems can be more sensitive to end-users.  There are many opportunities to infuse intelligence and friendliness into an interface, even if the only thing it wants you to do is press a few buttons.

The better news:  Nuance has experts in all kinds of telephone interaction design.  Working with a Nuance Business Consultant to evaluate your current systems is not a guarantee that we'll recommend converting to speech recognition.  Rather, we'll recommend what's right for your customers and for their goals.  All they might need is a little escalated error handling.