So you move to a big new city with tons of software development opportunity, having taken a six month contract-to-hire job. The company treats you really well and has a good team and work environment.
However, the recruiter assured you when offering the gig that it would be a good position in which you can advance your learning from more senior developers (a primary concern of yours) but you're starting to realize that a job recruiter isn't going to understand that the team in question isn't very up on modern software practices (you start to sympathize with this guy and read his post over and over again: http://stackoverflow.com/questions/1586166/career-killer-nhibernate-oop-design-patterns-domain-driven-design-test-driv) and that much of the company's software is very old and very very poorly architected, and the company (like so many others) seems to be only concerned with continually extending the software without investing in any structural improvements. You're absolutely dismayed at how long it takes your team (including) to fulfill simple feature requests (maybe 500-1000% longer than with better designed software that you've worked on in the past), but no one else there seems to think anything of it.
You find that the work and the company's business are intensely uninteresting to you, but due to the convoluted design of their various software systems, fulfilling the work will require as much mental engagement as any other development position.
You feel a bit naive about not having asked the right questions during your interview process, and for not having anticipated that your team at your former podunk company might possibly be light-years ahead of any team in Big Shiny City, but you know you don't want to stay at this place, and (were it not for your personal, after-hours studying and personal programming efforts) fear that you might actually give a worse interview after completing your 6 months than you did when you started at the place. You read about how hard of a time local companies are having filling their positions with qualified software development candidates. You read all sorts of fabulous sounding job postings online and feel like you're really missing out. In spite of the comfortable environment you feel like you would willingly accept a somewhat more demanding or aggressive lifestyle to feel like you are learning and progressing and producing something meaningful.
My questions are: how quickly do you leave and how do you go about giving a polite reason for departing? The contract is written to allow them to "can" you and to allow you to leave with 2 weeks notice. Do you ethically owe the 6 months? Upon taking the position, the company told you they were not interested in candidates who were intending to only stay for 6 months and then leave (you were not intending to bail after 6 months, at that time), so perhaps they might be fine if you split now, knowing that you don't want to stick around for the full time hire?