Will
 > >
 > > they are not the same in the way they can be accessed or manipulated  
 > > but their
 > > content is the same.
 > 
 > The more this is discussed the more I think that toks and tlp are fine  
 > names, and I wasn't thinking about changing them when I brought this up.

well you got me thinking on that level, because tlp could be named tlist to
fit with plist clist.

the problem seems to be more in the later addition of the \tlist functions
that in contrast to anything else do not operate on some storage bins but on
tokens in the input stream. 

 > I was just wondering if there was a short way to distinguish between  
 > what sort of material a toks and a tlp can contain. (I must have  
 > worded this particularly poorly.)
 > 
 > So in the documentation when we write
 > 
 >    \toks_set:Nn <toks> {<token list>}
 > 
 > cf.
 > 
 >    \tlp_set:Nn <tlp> {<token list>}

which is perfectly  correct as far as I can see. Am I dense?
... yes, ok I am, there is one difference in the handling of #. Anything else?

 > 
 > there might be some way of distinguishing the token list in the former  
 > compared to the latter.

what is the difference you want to distinguish in the content? As I said the
content is exactly the same (with the exception of #), it is only the
manipulation of it that differs, so

\tlp_set:Nn  \l_foo_tlp  {<token list>}
\toks_set:No \l_foo_toks { \tlp_use:N \l_foo_tlp }
\tlp_set:No  \l_foo_tlp  { \toks_use:N \l_foo_toks }

holds in as long as you don't have stray # chars

 > I'm still thinking there's nothing we can do but refer to the contents  
 > of both as "token lists" and just mention the differences at the  
 > beginning of l3tlp and l3toks.

probably; a quick read through the TeX book seems to indicate that Don also
didn't try to work this out in his BNF in both cases it is <balanced text>

frank