In order of appearance,
"Slide" - This is probably the most mediocre of Goo Goo Dolls' hit-songs. It's catchy, and a little bit "James Dean" in its attitude. It describes one of those unfortunate family-estranging young-love situations that usually don't end well, but hell if the participants would believe you had you told them that while they were at it. Wow, now that I think about it, this song actually kinda depresses me. o.O Anyway, it's one of those songs that's obviously going to continue to get radio play until well-after the band and all their original fans are dead, even if infrequenctly and only for the purposes of drumming-up nostalgia.
"Broadway" - For a song about spinning your wheels in a success-devoid music career while struggling with personal issues and the looming thought of your own mortality, this one is quite upbeat... Heh. Maybe the upbeat nature of the music is supposed to lend an element of sarcasm, or maybe it represents the "brave face" we all put-on in what seem like the worst of times. It's fun to listen to, and despite the subject matter, it's one of those that makes me eager to sing-along.
"Black Balloon" - This is one of those epic classics, IMO. Once you've heard and truly immersed your consciousness in the sounds of that intro, those dark, mournful and desolate tremolo-harmonics, it changes you. This is especially true if you hear it in high-fidelity audio, true as it can be to the original recording (thank you, MP3Caprice!) Anyway, the situation described is another hopelessly-doomed (and probably already over, given the past-tense language used) romance. It's about being dragged-down by someone you were trying to help. Considering the lines "you were the same as me, but on your knees..." at the beginning and "I'll become what you became to me" at the end, I think the idea is that the narrator (who may not necessarily have been John Rzeznick) is saying "I got into this trying to help you. Now I'm the one who needs fixing." According to Wikipedia, John said the song is about a woman with a heroin addiction. It makes sense that this song is about addiction to mind-altering substances, given the line "baby's black balloon makes her fly." This song conveys an energy which, even if you've never been in the situation about which it was written, you may well have been in one with the same energy.
"Iris" - Well, feck. What can anybody really say about "Iris"? To call it a true-rock-classic doesn't even come close to describing it. Its music was written with a soulful depth that just can't be replicated. The mandolin was a great choice. If I had one criticism towards this song, it's that the guitar solo could've been more exciting. It needs more 'flourishes.' That string-bend forming the first two or three of the last five or six notes at the end of the solo could have been preceded by several nearby notes, passed-over super-fast to lend it some complexity, for instance. That would have made that solo into pure-gold. If I were playing this song live, that's how I'd do it (or have the electric guitarist do it, anyway.) The acoustic guitar, even by itself, is totally magical. This song is totally unforgettable. I'm a guy with a massive vocabulary, who always has something to say about everything, but I myself have no words to fully describe its epicness.