I'm going to beat this dead horse with a bigger stick, because I've been thinking a lot about the arguments that support Danny going to Montana.
I agree that Danny is the type to support his friends 100%, but going to Montana is completely unlike his character. Yes, he's shown amazing passion in defending his friends, just as he did for Hawkes in "Raising Shane." But the difference here is that though Danny seemed to know a lot about Hawkes' everyday routine, and though he was frustrated to the point of anger at Hawkes' situation, he didn't do anything wildly unorthodox to help his coworker, either. He showed momentary defiance, but nothing like the grand production of flying across country to be with a "friend in need."
And as some people have already pointed out, the writers didn't go out of their way to show him in any great amount of emotional turmoil when his friend and long-time defender was lying in a hospital bed. Instead, they just let us assume that Danny was there for Flack. Well, I'd much rather ( and be far happier, in fact ) assume that Danny was supporting Lindsay -- from New York.
And though he showed amazing emotional depth and intensity at finding out Aiden had been murdered, I didn't see him taking any...shall we say, less-than-professional steps to find and bring her killer to justice. Far tamer than his early days in the first season, Danny was content to follow Mac's lead on that one -- and if rationality was the better part of discretion following the brutal murder of his close friend ( evidenced by the fact that they were still having dinner together from time to time ), why isn't it a factor in this decision to desperately follow Lindsay ( who he's known for far less time and obviously far less intimately, as she isn't too keen on dining with him as Aiden had done ) across the country?
Further, he didn't show anything like the cross-country flying gusto when it was Stella in the hospital, shakily explaining to Flack what her experiences in the apartment with the murderous Frankie were. The Danny that would fly to Montana seems to me like a Danny that wouldn't sit back and let Mac periodically give him updates on Stella's condition. From the pilot episode, it was clear that Danny and Stella had a special dynamic -- she coaxed and coached Danny through season one, and was a genuine friend and confessor to him in season two. And yet there were few indications that his concern was anywhere near as deep as the concern it would take someone to actually hop on a plane to Montana. Particularly when Danny still doesn't know why Lindsay's left. Remember: no one has clued him in -- all he knows is that she's left.
So I don't believe it's within his character to jump on a plane. In fact, I think for anyone's character, the move is extreme ( and taken, furthermore, right from an episode of All My Children ). I think the last time we saw that kind of intensity out of Danny was long before the days of Lindsay -- we're talking season one Danny. And even then, though the guy was a bit of a hot-head ( God, I miss those days ), I don't think we would have seen him do anything like this.
Those are simply my honest thoughts. I, for one, didn't ship Danny/Aiden, and I don't ship Danny/Lindsay. I think it's time for the writers to take a fresh approach with Danny AND Lindsay -- for one, they're killing Carmine's delicately cultivated Messer, and for two, they've done nothing for Lindsay independent of Danny. In a show that already revolves around the ( formerly ) hot-headed CSI, I hardly feel compelled to encourage more drama when so many other storylines for him have yet to be wrapped ( like his brother ). And isn't it about time something good happened to him? Why isn't he back on the promotion grid almost two seasons later?
So, bring on the Danny/Angell, or let the guy fly solo for a while -- in fact, why not have him being the player mastering the game? God knows it would be far more interesting than watching him flounder over the rest of this season, forcing with no small amount of lackluster a lust that isn't there.