So I've developed a medium-large Haskell project that used nearly - but not quite all - of those same extensions. I would never think to describe this as "a few lightweight GHC extensions". To me - and I think most others - it's just normal Haskell, but why even bring up "standardish" if this is what you do?
I got this list from a project involving a lot of people. If I'm in charge of the project the list gets much thinner :-)
Most of these extensions have been around for like 10 years now and are well understood. They integrate well with the language without impacting Haskell2010 code. For example, RankNTypes or any of the code gen ones.
I shouldn't have said "a few" though! There's lots of light extensions. The only ones I consider heavy are some of the type system ones, CPP and TemplateHaskell. TypeInType is the heaviest by far.
