"If you link to GPL code, then your code must as well be GPL."
That actually depends on a lot of things. This is only actually true if your work is a derivative work and linking a library does not automatically make this true 100% of the time or even 20% of the time. Ultimately a court makes that call but generally it's only true if your work and the library essentially have the same function such as a gui using the lib from a cli utility to make a graphical equivalent. An 200k line x86 emulator that links a 2k line unmodified zlib library to add the bonus of being able to read compressed images would not be a derivative and would only need a link back to the original lib.
Where people have issues is when the are deliberately trying to "get around" the GPL by say making a compression tool with some features lacking in gzip and only linking its libraries to try to separate out own code. Obviously this is a derivative and someone is trying to steal from the original authors, profiting from their work without paying them for it.
As I said:
"You actually have to modify the GPL'd code or incorporate it into your source AND distribute it before the GPL kicks in. The LGPL was created to spell this out in some cases but that doesn't mean the LGPL was actually needed in the first place, just that the LGPL makes it more explicit."
You might find speculation to the contrary but you won't find a court ruling on any piece of GPL'd code counter to what I've said here.
"Of course, if you're only using this code internally, that is just a technicality, but linking to a GPL library means you potentially have a lot of work on your hands if you ever decide to commercialize your internal code."
If you are using code internally the terms of the GPL don't matter. The mere use of software does not require a license as copyright law does not grant the right to restrict usage. And the GPL allows commercial distribution. It simply requires you make the source available (of your modifications) along with the sale and with GPL v3 all the patent rights required for the next person in line to do the same.