BSB music is the best for road trips!
IAWLT is still my favorite of their albums, with Millennium as a close second, like you. I used to put Never Gone up there too, but I don't think its songs have stood the test of time as well as Millennium's for me. I think my least favorite album is still This is Us (with that horrid PDA song and the one about Shorty LOL). Black & Blue is in the bottom half of my list too, though. For as many good songs as there are on that album, there are also a lot of duds. That's how I feel about This is Us and Unbreakable, too.
Anyway, going back to IAWLT, the only skip song I have is still Try. I still love the rest of the songs, although I think my favorites have changed a little. I found my original rankings on p. 20 of this thread, and I had originally put Soldier and Show 'Em as my top 2. I still love both those songs, but now I'd probably say One Phone Call (sorry, Mare) and Take Care. The song In a World Like This would still be way up there; it will probably always be one of my favorite singles. Love Somebody would be higher on my list now than it was then; I think seeing them perform that one in concert made me love it twice as much.
I am ready for new music, though! Even though Nick has released two albums in two years, the last couple years have been pretty slow in terms of BSB. I'm feeling the lack of a tour this summer. I know they're working on it; I just wish they'd work a little faster!