You are correct on all counts.

Version 10 has Association which provides a means to get Keys and Values separately, amongst numerous other features. It too has a hash table under the hood. One caveat is it might not be as useful if one plans to build it up or modify in many steps.

Check the documentation for DownValues, Set, and Unset. For things that are free of explicit patterns, something like

myTable[key1] = val1;
myTable[key2] = val2;

is effectively a hash table with key and key2 as keys, etc. (and they really are hashed, under the hood). To remove one of these use Unset; I show the infix version below.

myTable[key1] = val1;                                                   
myTable[key2] = val2;               

We look up key:

In[9]:= myTable[key1]                                                           

Out[9]= val1

Now clear it and try that lookup. It will fail to find a value.

In[10]:=  myTable[key1] =.                                                      

In[11]:= myTable[key1]                                                          

Out[11]= myTable[key1]