Leksah may be worth trying because:

• It uses the cabal package format and incorporates a cabal file editor
• It offers Workspaces for complex project with multiple packages with automatic build of dependencies
• It contains a module browser that allows you to find type information about all the functions/symbols available in the packages installed on your system
• For most packages it shows as well haddock style comments, and give direct navigation to sources
• It integrates ghci debugging (including continuous recompilation) that allows you to type check and evaluate highlighted code snippets from within the editor itself. Includes a scratch buffer for testing ideas
• It includes an helper for automatic addition of import statements
• Offers a Haskell customised editor with "source candy"
• Multi-window support for a multi head setting
• Many standard features of IDEs like: Jump to errors, Auto Completion, Grep integration, ...
• Configurable with session support, keymaps and flexible appearance