Man, this debate is old as the hills. Seems to me the whole "Christian music isn't good" argument boils down to 1) the person making the statement hasn't heard good Christian music or 2) the person making the statement doesn't want to listen to Christian music. I know people who will listen to the music playing in my car, think it's great, then ask who it is--when they find out it's Christian, it goes from good to okay, but [insert popular secular group here] is better.
Switchfoot, Kutless, Tourniquet, ZOEgirl, Rebecca St. James, Toby Mac, CeCe Winans--they're all as good as at least 75% of what's on top 100 radio, and in most cases, people who've never heard them wouldn't know they were Chrsitian if it weren't for the lyrical message. Good or bad is so qualitative anyway, who's to say one band's music is better than another's? It's all a matter of opinion and conjecture.
Is it okay to listen to secular music? Why not? I guess it really depends on what you're listening to. If it's a steady diet of f-bombs, sexual degredation, and violence, then you probably ought to be asking yourself why you're listening to it in the first place. If it's something that doesn't conflict with God's word--and there's a lot of secular music out there that doesn't, despite what some of the CCM zealots would have you believe--then why deprive yourself of it?
Don't think that the music you listen to doesn't affect you. It does. Human psychology is so fragile. Almost everything you read, watch, and listen to has an affect on you. Ever read the scripture, faith comes by hearing? God programmed us, He knows what we need and that's why He gives us guidelines. It's also another reason for daily Bible reading. Somebody once said that reading the Bible is like giving your spirit a bath--at the very least, recentering your thoughts on God. To me, that's what true Chrsitian music does. It centers your thoughts on God. It creates and attitude of worship and spiritual reflection.