Radio 104.5 does well because it's on a great signal, it's well promoted, and it's the only "Alternative" station in Philly (I put "Alternative" in quotes because they play a lot of acts that don't fit the format: The Fray, All American Rejects, and Blues Traveler to name a few). Don't think for a second that they're only successful because they're taking a safe, hit-intensive approach to the format - they have a lot going for them with this signal. One can only imagine how well WDRE or even Y-100 would have done on a signal like this ... and to be honest, the only way Radio One ended Y-100 is for the same reason Press dropped G Rock and Atlantic killed WJSE: hatred for the format, which they tried to cover up by claiming they couldn't make it profitable.
Believe it or not, there's some people who don't like a station that sounds like a really tiny jukebox with some droning guy between songs. Maybe people would like a happy medium between the constant yakking on 'MMR and the near-silence from the "personalities" on Radio 104.5 ... and maybe they would like a station that realizes that, yes, one can only hear "Smells Like Teen Spirit", "Under The Bridge", "Lightning Crashes" and all the tired songs from Pearl Jam's Ten so many times before you feel like screaming.
If it wasn't for the relatively limited competition in the market, I could see someone else trying an alternative format in the market: with more than just 15-20 Currents, 300-400 Gold titles, and allows their DJs to say more than just artist names, song titles and tour dates. And if you gave this station some time, I think it could top Radio 104.5. Alternative rock fans are a different breed - they're not looking to hear "just the hits". And if we had some new blood in the market willing to give a more daring take on the format a shot, that would prove my point.