Since this is a first impression review, I will only review my first impressions. I think I will have more profound impressions after using this for a few weeks during those workhorse writing sessions...
Appearance/Finish:
Initially I was a little anxious about the faceted body since I have always used a cylindrical barrel all my life but it is actually quite comfortable. The Arco is as reported here: depending on the angle and light, it is quite subtle. There is some of those Japanese "gold-leaf" aesthetic to it. Since this is my first celluloid pen--I have always been a metal pen person until I hit this board: "bad" influence

Size/Weight:
I have heard some remarked that the pen is heavy. A few minutes of use, and compared side by side with the Emotica informed me that the Emotica actually feels heftier. The Paragon is slightly longer and wider than the Emotica but not by much (and my Emotica is black, so it should 'look' more compact visually). Some remarked before that this new Arte Italiana with the new metal section writes on its own weight. I feel that this is almost instinctively true at first use but what is remarkable about this pen is that after a few minutes of writing, it is neither end nor top heavy: it is really quite well-balanced! Compared to the Emotica, this pen when posted is top heavy making it uncomfortable for long sessions.
Filling System:
Piston filled. Also my first piston filled pen. It is not completely smooth but you feel a nice tactile 'turning' effect to it as you turn it. Whether this is normal or not awaits more use. But I can see myself using this for quite a while before refilling: 2.6ml!
I should also add that posting in this pen seems to interfere with the piston knob. When trying to unpost, there is a tendency to turn the knob. Maybe this is a piston filled pen problem?
Nib:
Ah...I wrote side by side with the Emotica F Ti nib. I think Mike S's description on the Emotica is right on: teflon smooth--a very nice tactile feel as you write. The F nib on the Arco on the other hand is very smooth, but not Namiki buttery smooth like. Depending on the pressure and angle you exert on the paper, it feels different but it has a feel to it. As compared to the Namiki broad I have, you feel that this is something that becomes a part of your writing hand, while the Namiki still feels like an instrument that slowly dissolves into the background. They are both nice but the Omas has a nice tactile yet smooth feel to it while the Namiki is nearly 'effortless' (caveat: I am using different inks: Omas Noodler's and Namiki: PR). On a grade of 0 to 10, 0 being buttery smooth nearing unity between pen and paper and 10 being the most toothy, the Namiki gets 1 and the Ti nib gets 7 while the Arco gets 5. I think I still like my Emotica nib better from the tactility than the gold nib of the Arco but we shall see!

Conclusion:
On first impression and upon a short writing session, this is an extremely well-made pen. I thought it might be bling-bling but it is actually quite subdued under normal lighting. But once under near yellow light, I think it might be bling-bling because of the golden reflection of the Arco. I think this is also my last pen for a while and I will look into customized nib from now given the nice comments I get from my students on how my hand writing looks with a music nib!
I purchased this pen from Bromfield Pens in Boston, a very nice pen shop I visited every few weeks when I lived there and the transaction was very pleasant and smooth. I should have received this pen sooner if not for the storm that just plagued the northeast.
Happy!