Prior to the popular Agile era which started roughly in the late 90's, The waterfall model was widely recognized as the most popular, and involved a  sequential software design process, in which progress is seen as flowing steadily downwards (like a waterfall) through the phases of Conception, Initiation, Analysis, Design, Construction, Testing, Production/Implementation and Maintenance.
The down-sides included time-lines and budgets.  A typical software build could take 6 to 9 months, during which time the stakeholder had little or no interaction with the product and what seemed to be business critical at the start of the build would often be deemed unnecessary or secondary months later. The client also realized no benefit from the project until the very end when the entire system was presented in one wave- not always the all-singing, all-dancing system it might have been sold as.

The four core values of agile software development as stated by the Agile Manifesto emphasize: Individuals and interactions over processes and tools. Working software over comprehensive documentation. Customer collaboration over contract negotiation.

The Agile Manifesto, above,  evolved processes somewhat and gives the stakeholder a greater level of control at a much earlier phase of the build time-line. As functionality is released, it can delivered incrementally, enabling some benefits to be realized early as the product continues to develop. This Speed-to-market can be beneficial for cost control and monitoring quality before it's too late to do anything about it. Should requirements alter, subsequent functionality and system design can be changed before being developed, saving large amounts of wasted development costs. The end result is optimum business Engagement and Customer Satisfaction.

Agile is not without its own challenges though... with daily stand up meetings not always being possible and regular involvement from stakeholders can be limited due to time and distance. Business Analysis, Requirements Planning and Estimates might not always be totally accurate and can change along the way, proving to slow down development and be seen by developers as a distraction.
Ask any developer using Agile, they would still rather not have estimates and planning around every corner and the #noestimates movement is gaining momentum, adding the need for even better tools to unsure that quality is not compromised by frequent delivery dates.The #NoEstimates hash tag on twitter has caused a whirlwind of discussion about the role of estimates in software development, with several books already writtenon the subject.

The basic idea, is that it is possible to do small chunks of work incrementally, leading as rapidly as possible to a desired usable product, and that when you do that there is no need to do much of anything in the way of estimating stories or the project. Estimates present another challenge all together. When requirements are vague — and it seems that they always are — then the best conceivable estimates could also be guestimates rather than estimates. Accurate estimation of complex functionality often requires a fair amount of work and quite frequently some initial coding to validate. It is still almost impossible to know how long something will take, without research and validation.

Estimation is challenging and we would be well off if we could avoid it, that’s why the #NoEstimates idea is so compelling, however there are many real business questions that will always need to be answered before they become obsolete. “When will it be ready?” “How much will it cost?”
“Accurate estimation is impossible for complex technical projects, but keeping to agreed budgets and deadlines is achievable by using feedback and change.” Seb Rose from Clay Snow

George Toursoulopoulos, CEO at Synetec Ltd, who delivers bespoke software to small and medium size hedge funds is aware of his development team shouting No Estimates, yet insists that his clients require commitment in terms of deliverables and costs and estimates are currently still essential.

George Toursoulopoulos is a technology specialist and CEO of Synetec, one of the UK’s leading providers of bespoke software solutions.