How to setup vim properly for editing in utf-8 - vim

Question

I've run into problems a few times because vim's encoding was set to latin1 by default and I didn't notice and assumed it was using utf-8. Now that I have, I'd like to set up vim so that it will do the right thing in all obvious cases, and use utf-8 by default.
What I'd like to avoid:
Forcing a file saved in some other encoding that would have worked before my changes to open as utf-8, resulting in gibberish.
Forcing a terminal that doesn't support multibyte characters (like the Windows XP one) to try to display them anyway, resulting in gibberish.
Interfering with other programs' ability to read or edit the files (I have a (perhaps unjustified) aversion to using a BOM by default because I am unclear on how likely it is to mess other programs up.)
Other issues that I don't know enough about to guess at (but hopefully you do!)
What I've got so far:
if has("multi_byte")
if &termencoding == ""
let &termencoding = &encoding
endif
set encoding=utf-8 " better default than latin1
setglobal fileencoding=utf-8 " change default file encoding when writing new files
"setglobal bomb " use a BOM when writing new files
set fileencodings=ucs-bom,utf-8,latin1 " order to check for encodings when reading files
endif
This is taken and slightly modified from the vim wiki. I moved the bomb from setglobal fileencoding to its own statement because otherwise it doesn't actually work. I also commented out that line because of my uncertainty towards BOMs.
What I'm looking for:
Possible pitfalls to avoid that I missed
Problems with the existing code
Links to anywhere this has been discussed / set out already
Ultimately, I'd like this to result in a no-thought-required copy/paste snippet that will set up vim for utf-8-by-default that will work across platforms.
EDIT: I've marked my own answer as accepted for now, as far as I can tell it works okay and accounts for all things it can reasonably account for. But it's not set in stone; if you have any new information please feel free to answer!

Answer 1

In response to sehe, I'll give a go at answering my own question! I removed the updates I made to the original question and have moved them to this answer. This is probably the better way to do it.
The answer:
if has("multi_byte")
if &termencoding == ""
let &termencoding = &encoding
endif
set encoding=utf-8 " better default than latin1
setglobal fileencoding=utf-8 " change default file encoding when writing new files
endif
I removed the bomb line because according to the BOM Wikipedia page it is not needed when using utf-8 and in fact defeats ASCII backwards compatibility. As long as ucs-bom is first in fileencodings, vim will be able to detect and handle existing files with BOMs, so it is not needed for that either.
I removed the fileencodings line because it is not needed in this case. From the Vim docs: When 'encoding' is set to a Unicode encoding, and 'fileencodings' was not set yet, the default for 'fileencodings' is changed.
I am using setglobal filencoding (as opposed to set fileencoding) because:
When reading a file, fileencoding will be automatically set based on fileencodings. So it only matters for new files then. And according to the docs again:
For a new file the global value of
'fileencoding' is used.

Answer 2

I think it would suffice to have a vanilla vimrc + fenc=utf-8
The rest should be pretty decent out-of-the-box
I'd use the BOM only on Windows platforms with Microsoft tooling (although even some of these fail to always write a BOM; however it is the default for Notepad Unicode saving, .NET XmlWriter and other central points of the MS platform tools)