Sorry to jump on the bandwagon so late!
a) Danny's looks: TPTB played him for maximun beefcake benefit (which I'm sure did wonders for the ratings on the West coast once the East coast fans started squeeing!! on-line). As for the clothes, I do seem to recall he commented on the price of the t-shirts the guy was selling in the first Shane epi as them being too expensive for his salary. On the other hand, there's the green shirt... which has been seen on more than one ep already.
b) Character: we got the watered-down, I'm-trying-to-be-mature, see-Lindsay-I'm-not-really-a-player-nor-a-dog Danny Messer for some 85% of the season (I have the final four eps to watch yet, so please let me have some hope). But he did have some shining moments... or am I the only one who went awww when they heard his "I'm-scared-sh***ess" waver in his voice in the second Shane epi?
c)The Romance: a tad too high-school for my tastes. And TPTB were definitively going for pleasing the female fans with that whole arch. On behalf of TPTB, they also tried appealing an older crowd with the Mac/Peyton storyline, which hasn't been entirely succesful (too many people too gung ho on Mac and Stella together, I guess).
Seen from an entirely business-like view, they played the right card: just check out sites like TV.com or FanFiction.net and you'll see that 9 out of 10 CSI NY fan is a die-hard D/L shipper (or M&M's lover, whichever you prefer). To be perfectly honest, this is the first site I've bumped into that is not overly rooting for that ship.
And so it comes, confession time: I plead guilty to having written D/L fanfic although it's not the ship I pledge (all the Flac/Stella shippers in da house go OH-OH... sorry.. got carried away there for a sec). Now, why on Earth, do you ask, did I do something like that? Cause sadly, my dears, that's the only way to get into the CSI NY fanfic world and get acknowledged/reviewed/taken into account. Alas, now that I'm some sort of "established" author (snort!snort!) I'm writing what I like, which is definitively NON-cannon.
Let's just hope next season gives us a better Danny!