Updated Preparing your system to use Stackage (markdown)

Preparing-your-system-to-use-Stackage.md

@@ -84,7 +84,9 @@ You have the following options when switching to a new snapshot:
     1. Updating your `~/.cabal/config` file with a new remote-repo.
     2. Deleting your `~/.ghc` directory.
     3. Running `cabal update`
-2. Switch in a sandbox. You can currently use `hsenv` to do that. cabal sandboxes are currently limited
+2. Switch in a sandbox. You can currently use `hsenv` to do that. cabal sandboxes [currently don't support overriding remote-repo](https://github.com/haskell/cabal/issues/1884).
+
+Note that these instructions also apply for migrating from an older Stackage snapshot to a new one.
 
 ### Using a cabal.config file (simplest usage)
 
@@ -118,4 +120,4 @@ Stackage Server is designed to work either with or without Haskell Platform. The
 * On Mac OS X, there are complications regarding the correct CPP toolchain to get set up. There are some scripts available to help, but the Haskell Platform provides a fully functioning toolset. Like Windows, you're likely safer sticking with Haskell Platform.
 *   The biggest downside of Haskell Platform is that it ties you to older versions of dependencies. The biggest two examples in the current platform release are attoparsec and QuickCheck. For the former, the version included by Haskell Platform has a known security vulnerability. The QuickCheck version included is before a major API change, which a number of packages are beginning to use.
 
-    The choice is yours, but my advice for users not on Windows or Mac is to not use Haskell Platform.
+    The choice is yours, but my advice for users not on Windows or Mac is to not use Haskell Platform.