Any Room for a Gaijin?

Over the last few months I've been doing some leg work in order to find employment in Japan.  I'll be getting married to a Japanese woman in just over a year, so it only makes sense that I get myself a job over there in order to provide, right?

When I talk to people here in Canada about finding work in Japan, I'm told that it will be relatively simple.  As a foreigner, I'll have my choice of careers where native English is a key skill that can set me apart from the rest.  Well … that's what I'm told.

When I discuss this with people who are living in Japan (not only my fiancee, but other people from various parts of the globe), I'm told that it's not half as easy as one would think.  Not only is there the legal paperwork to get out of the way (work visas are apparently quite limiting and requires that I have a sponsor before actually getting the position in the company), but there's also the rather large corporate culture differences.  I've spoken to more than one programmer who worked in Japan for over five years, and spent the first three running errands and cleaning toilets instead of writing code.

Could I do the same without feeling frustrated by the lack of mental stimulation?  I'm really curious to know just how common this scenario is.

I understand that immigrants to any nation typically do the jobs that nobody else wants to do.  Because an immigrant moves to a country with goals of a better life for them and their children (usually), should I expect the same type of scenario?  Either way, I'll be over there in a matter of years.  Sooner if I can manage it.

Does anyone have any experience with this?  I'd be interested to know what difficulties (if any) you've faced.