To clarify David's point about legibility of the unified Han, one of the
heuristics used in unification was that the maximum range of glyph
variation allowed in the unification of characters from different standards
should be no greater than the maximum variation acceptable within any one
standard. For example, JIS standards X 0208 and X 0212 both list the range
range of glyph variation deemed acceptable for unification in a single code
point. This can be found in section 3.6 of the explanatory material.The
discussion shows that JIS itself unifies "minor variations" (wazukana
tigai). Chart 6 on page 74 of JIS X 0208-1990 illustrates these variations.
If you compare the unified Han in 10646 with the JIS chart, you will find
that the results of Han unification fall within the tolerance of the
"wazukana tigai" discussed in JIS. This is not surprising since virtually
the same set of distinctions exist and are recognized as "minor" by some
group of people in each of the CJK countries. If anything, the requirement
for a round trip mapping caused the CJK-JRG to err on the side of
disunification.
The problem, then, is not whether an individual accepts the
CJK-unifications in Unicode and 10646 as identical characters, but whether
he or she accepts the unifications implemented by the national standard
bodies in existing standards in his or her respective country. There are
Japanese who agree with JIS on the "wazukana tigai" and Japanese who don't.
Those who agree accept Han unification, the others don't.
I see little point for this group to continue to debate whether 10646
satisfies a requirement that no other encoding, including JIS, even
attempts or claims to satisfy.
Lee