One might say it's slower then a spreadsheet. I don't know. I can type an one liner awk summation/average, faster then it takes OpenOffice to load. This is to me the most common spreadsheet operation.
For more complex task, I feel that I'm working faster in awk (it's a full blown high level programming language, after all). I'm not sure it it's actually faster or if it's only my opinion though.
I'm happy with this setup.
In the event that I need a visual prototype to work with, together with a client or business partner, I don't think it's all that horrible to prototype something in Excel, and later port it to Haskell if necessary. But that's of course because I already, at some point, reinvented the wheel to make this possible. So now I'm mostly just reusing code which I already have available.
That said: strings are lists of chars, and Haskell is strong at pattern matching (esp within lists) in a bunch of different ways, so trivial text parsing tasks are trivial and intuitive in Haskell. For anything slightly more complex, there are regular expression and enumerating libraries which can do the job alright (and efficiently if I may say so).
EDIT: I'm sorry, can you give me an example of a problem so I can give you an example of a solution? :-)