Currently I'm finishing my master program in computing. I need to decide between going to industry and starting a PhD programme. Having worked a bit with research and industry I prefer the former so far, however I wouldn't like to close my career paths.
Is it hard to resume education after working in industry (assuming 'ideal' conditions such as work related to chosen field, good master project from good university etc.)?
One thing that hasn't been mentioned in the answers to this question pertain to recommendation letters, which are a key and important part of the application process. If you decide to leave academia for an extended period (more than a year or two), it would be wise to keep in touch with your advisor and some other professors so you don't surprise them with a "could write me a letter of recommendation for a PhD program" many years down the road. They need to be able to comment explicitly on your potential to do research, and (for U.S. universities) you'll need three solid letters to be competitive.
I might suggest asking for letters of recommendation now, and plan on contacting your letter-writers later to ask them to look back over the letters, and update if necessary. This way they aren't scratching their heads trying to (1) remember you, and (2) write a quality letter a few years after they knew you and your research.
By the way, I started a Master's/PhD program about 15 years after I got my Bachelor's (and another Master's in a different field), and finding appropriate and relevant letter-writers did prove a bit challenging. I ended up getting a letter from my then-boss (science department chair at the high school where I taught physics), a professor of education from my previous Master's degree, and a physics professor with whom I had been taking some "physics pedagogy" classes (and all for degree programs in computer engineering!). In the end, I successfully got accepted into many of the schools I applied to, but I'm sure my case would have been helped if I had letters that commented more specifically on my ability to research.