I really enjoyed it - it was a really friendly workplace, and everyone was willing to help if I was stuck on a problem. The work was challenging but interesting, and as the projects developed I was able to work more autonomously, which is a freedom that is rare for an internship.
I am still not entirely sure that I want to pursue a career in software but I can't imagine anywhere better to do so than Metaswitch. The office space has a good atmosphere, the employees are friendly and helpful and there are many other benefits available to vacation students such as local accommodation in company owned housing and frequent events funded by the morale team.
The work was interesting and worthwhile as the project you work on is uesful and will not get forgotten about as soon as you leave. There is a nice working atmosphere - free biscuits in the kitchens and occasional morale trips out of work. There are often drinks in the local pubs on the company tab for people's birthdays, new starters, etc. There are also lots of other interns (about 30 in 2010).