Yes, the date handling currently has some flaws.  It does not handle the concept of "Between" and it has some problems with partial dates (when no year is specified).  It does handle "Before", "After", "Est", "Circa" and the like.  Ranges will just take a little longer to implement, especially since they can have impact on sorting.

Partial dates just need to be handled better.  They are currently buggy.
On 06 May 2001 16:01:22 -0400, Howard Holm wrote:
> On 05 May 2001 08:08:11 -0600, Don Allingham wrote:
> > gramps-0.1.3 has been released. In addition to fixed some bugs, it adds
> > support for the ISO-8859-1 character and ANSEL encoding in GEDCOM files.
> > This should allow gramps to be used with languages other than english.
> I haven't had much time to play with the program but one pretty serious
> issue I noticed right away.  The program has a very limited view of what
> a date is.  A date could be a range.  GEDCOM standard dates include
> notions of between, after, and before at least (IIRC.)  I attempted a
> pretty standard "partial date" of day and month for a birthday (assuming
> the the source I was using didn't have the year.  The program seemed to
> accept it, but then silently threw away the input.  Silently altering
> the input of someone carefully copying from a source is a sure way to
> annoy people.
Don Allingham