Regarding the Argonians, I have this. While I think that their reusing of the animations and meshes in Oblivion was unoriginal, I didn't really mind too much, because there was a lot of stuff put in. Gameplay-wise, they could both wear boots now and had permanent water breathing. I also thought it was cool that the male and female were completely different colors. But that's just my take on it.
The permanent water breating could have easily been done in Morrowind as well but was simply left out because one quest included drowing yourself (though they could have done water breathing toggleable or put in a script that deactivates permanent water breathing for that mission) and, honestly, the "they can wear boots" thing is the lowest argument (nothing aimed against you, it just always annoyed me) since MODDERS made leggings for the beast races in Morrowind. Beth could have easily made something like that too.
They didn't "fix" anything about them they just patched over it. Good example are the helmets, a common complaint was that beast races coudln't wear full helmets but, oh so great, they could in Oblivion. But this wasn't fixed as all full helmets did was still replace the characters head and replace it with the helmet mesh, this became very obvious when you had an argonian char with a longer snout as it was uddenly cut away by the helmet.
And that's another annoyance about the new design, the faces are so FLAT. I actually looked at the base mesh they used and it looks HORRIBLE, sometihng like Tim Burton would think off maybe...
Also in FaceGen you couldn't really give them good faces, they all just looked deformed and you couldn't really change the eyes.
All together they could and SHOULD have done a lot better... clearly my most dissapointing discovery...
EDIT:
Plus what ThatOneGuy said about "holding back" their design till the very last minute, doubt it was for the "big surprise" effect but rather to hold back the rage of fans for as long as possible, or so ideas for improvements could be smacked back with "it's to late now to do big changes.
Oh yea and Male and Female argonians in Morrowind DID have different colors as well, not as much different as in Oblivion though. But again that was nothing that couldn't have been done easily by just chaning the coloration or saturation in a graphic program, i could do that in 5 minutes in photoshop.