Negatives to a .xlsm file?

I presume your question relates to negative about a .xlsm file per se rather than negatives about naming the computer in a macro.

The only small negative I can think of is that depending on how someone's Excel settings are parameterised the user will be prompted on opening the file to say whether they want the macros to be enabled. A No answer will still open the file but the macros won;t run. Some see this as a disadvantage for users who may not have a clue what the implications of 'Do you want to enable macros' might be.

Otherwise I can see no other disadvantage. And if you have large workbooks there are advantages to using a .xlsb file extension.

I was interested in your comment that you al use a shared document but only one can edit and save.

Do you mean that you are using the Workbook Sharing functionality? This allows many users to change things but where there is a conflict the system requires someone to arbitrate before which of two or more changes to the same cell(s) should take precedence.

Or did you simply mean that many users open the workbook but the second and subsequent users can only open in Read Only mode.

Yes there are ways to turn off the warning, but proceed with caution. The warning is there for a reason.

In the File, Options, Trust Centre, Trust Centre Settings, Macro Settings menu you end up with four options.

Unfortunately these are Application Settings not specific workbook settings so wil apply to All Macros in all open workbooks. The risk is someone opens a different workbook which might contain malicious macros.

The other way is to set up a Trusted Location - See the Trust Centre Settings Menu and put the file therein.