From what I have seen in real life is that they can be used interchangeably in general writing, however I suspect there is correct and incorrect usages.

Anyone know more about this?

Yellowbridge and Wiktionary both say they're just variants of one another:

http://www.yellowbridge.com/chinese/charsearch.php?searchChinese=1&zi=%E9%BA%BD

http://en.wiktionary.org/wiki/%E9%BA%BC

[links are probably munged, sorry]

James

In Taiwan second one only seems is used.
I some time ago had same question, and asked, and got answer - here we use second one only

The textbook I am using to study at university in Taiwan uses both, ie it uses
什麽 and 怎麼樣。

The auto complete on the Mac OS X input method auto selected the different "me" as per what my textbook says as well.

As usual I'm hoping for pts to weigh in. ;)

什麼 怎麼樣 - just wrote it using google pinyin
I got 麼 in both cases

Only 麼 but not 麽 is listed in the online dictionary http://dict.revised.moe.edu.tw/ provided by the Taiwan MOE.

康熙字典 quoted another dictionary: 《正字通》下從幺。俗作么，誤。(正字通 said that the bottom component is 幺. It is commonly written incorrectly as 么.)

Very good point, I didn't think to check that dictionary. I agree, this means kids are going to be taught to only use 麼.