If WDRE came back, I would definitely listen. If Philly can support as many rock stations as it does, it's not hard to see 'DRE making a return, taking listeners from the competition and winning support from those who have become disillusioned with radio.
I've tried listening to Radio 104.5 on several occasions. And honestly, you would be hard-pressed to find a safer, more hit-driven "Alternative" station than them. Because they play so many of the same old familiar songs and have so much overlap between them and the mainstream rock and Hot AC stations, it's extremely frustrating to listen to. Not much '80s music (when they do play it, it's the big arena-rock songs from The Clash and U2), a lot of '90s songs that everyone is sick of by now (seriously, haven't we heard "Smells Like Teen Spirit", "Even Flow", "Lightning Crashes" and "Interstate Love Song" enough already?), and a lot of bands that really don't belong on an Alternative station (The Fray, 3 Doors Down, The All American Rejects, Blues Traveler, post-A Boy Named Goo Goo Goo Dolls, etc.). Worst of all, the playlist is extremely small, with perhaps 300-400 songs on it by my estimate ... that's about half the size of the playlist of the late, lamented G Rock 106.3/106.5. For a station that de-emphasizes DJ banter and limits most talk to backselling the songs, having such a tiny playlist doesn't make sense. It may be doing well now, but it won't stay that way if it continues such a safe approach, or if competition emerges.
The rock market is crowded, but every station right now is very safe and predictable. WMMR is pretty much bulletproof, but the other stations are fair game. If WDRE returns and "dares to be different", it will benefit from having stale competition. I believe that radio should offer something that you can't get from other sources, and to that end, WDRE would be smart not to alter its approach ... the listeners will flock to it over a station that sounds like a really safe 1 GB iPod with commercials.