Dongmin,
You know what, I completely agree. I remember reading all kinds of articles on the technology back in the day and haven't seen practically any of it realized. Bluetooth is like molasses it seems. Especially compared to other technologies out there. I get the whole "it hasn't been accepted enough" argument, but still, wouldn't something be a whole lot more accepted if companies would put out cool pieces of tech that used it.
I look forward to the day where I can get some bluetooth speakers. That would be sweet. I suppose I kind of see why speakers haven't come out yet. Have you ever transferred a MP3 from one bluetooth equipped mac to another. My GOD talk about slow! Can you imagine a WAV file! Compared to 802.11b or g you'll feel like youre back in the stone ages. So I imagine that unless they find some way to seriously compress whatever signal would have to be sent to the speakers (hmmm wouldn't that be an analog signal?...interesting) you'd either be hearing some seriously degraded music or maybe you'd have to wait awhile...or maybe I have no idea what the hell I'm talkin about.
Besides that I'm pretty much wireless already. When I got my new powerbook I also got the Airport extreme and connected my printer to the USB port on that, which makes for wireless printing and wireless ethernet. I got a bluetooth mouse and keyboard. So other than that I just have to plug in the AC adapter and I'm good to go.
I have speakers which I plug in once in awhile and a scanner which I have to plug in very rarely as well. Though it would be nice to go wireless with these, its a pretty minor inconvenience.
So Dongmin, if you decide to maybe go my route to make your life a bit easier, just one word of warning, be very careful what printer you get for the airport extreme. Its only compatible with certain ones. Theres a list somewhere on apples site. Yeah, I mention this cause I had to send a printer back because of it.
Lastly, this is kind of interesting to note. My printer is that HP 995C bluetooth printer. I got it about 1 and a half years ago. I think it was the first one to come out with bluetooth already in it. Course I don't use that bluetooth function at all (I got it to work one time with my Compaq Ipaq) , but its kind of funny that it has bluetooth but I'm using it wirelessly with 802.11g instead. Yep, What a good old fashion waste of money that bluetooth function was. Oh well.
I got very lucky that it happened to be compatible with the Airport Extreme USB printer.
Hope I helped give you some options.