It seems that the first task I am set to with new clients is briefly summarising what a content managed system actually does, why it would be a benefit to them and why I personally push for an open source approach. In all honesty they seem to take on board the benefits I reel off (I do tailor them to the particular client), but generally they are bought when you advise on cost comparisons. Its really simple, an open source, mature content management system is going to be far cheaper than developing a custom system, or purchasing a licensed application.
From a developers point of view, what does makes open source so good, and why Drupal in particular, when there are so many open source options? This is a question I ask myself regularly, as not to get too surrounded by one particular application. But despite my best efforts I always do get surrounded and submerged in Drupal. Above and beyond all the other open source options, I find this to be the most flexible and extendable system available.
Once you get over the incredibly steep (and getting steeper) learning curve, actual hands on dirty development, designing and production is a hassle free, and dare I say enjoyable experience. The Drupal community is a very strong and active one, regular discussions, updates and progressions are being made on a daily basis, it really is a buzzing environment to be part of. The end result is a constantly evolving, expanding application, that I have been able to use for kinds of sites including blogs, community driven sites, corporate builds, forums, social and events based sites, secure data archiving sites, content and media rich sites and brochure and ecommerce sites, I have even built content managed full flash websites. Not a bad return for a 'free' application.
Over the last 5 years, I have worked with numerous Drupal projects, it has such a limitless supply of addition modules and enhancements, that to date I have never encountered an issue or function that has either never been encountered before, or a module is not available to create the function, or in the worse case scenario a problem has been encountered and I have to re-work a module to squeeze the result I want from it. This gives me great confidence in the application and this confidence is then transmitted to my clients, thus creating a very positive working relationship.
Plus, if its good enough for the most powerful man in the world, I guess its good enough for me too!!