I do like it for several reasons.
1) If I am waiting for a really important call, and am on the phone, I can jump off. This means less potential for phone-tag on an issue that I need to resolve. Usually I will let person #1 know "Hey, I'm waiting for the doctor to call so if I jump off the call I'll get back to you". This should be sufficient warning for most people and doesn't leave them thinking you're a jerk, or incontinent, if you suddenly burst out "GOTTAGO!!", and also you get to find out you don't have the clap or something like that and can move on with your life. I also use the pre-call-cut-short notice when I am approaching a tunnel. Yes. While talking in the car. Lovely.
2) If I am the caller, and the callee is on the other line, the ring sounds different. This is when I hang up the phone (at least when I am calling a cell phone, which I usually am). 99.9% of the time the person I was calling saw my name pop up during their other conversation and will return my call. No one is unduly interrupted and all necessary conversations take place. Beautiful.
3) If I am stuck on a call with my father, who drives me fucking insane and with whom I try to avoid conversations at all costs, and another call is coming in I can say "Oh crap, work is calling, I gotta go!!". Even if it's just the hair salon reminding me of my appointment tomorrow. The economy is tough; if "work is calling" you can't fuck with that. I'm not too worried about being rude here because most likely I'm ready to kill him anyway. Sweet.
So, given all those things I appreciate about call waiting there are a few negatives that drive me. Effing. Nuts.
1) Typically only older people do this. Usually moms (not mine!!) or grandmothers or mothers-in-law (no hate, just a fact). You call them and they're on the other line and before you can hang up they switch over, almost out of breath with the excitement of it all, and instantly declare "I'M ON THE OTHER LINE - I HAVE TO CALL YOU BACK!!!". Or my mom's personal favorite "I'M AT STOP AND SHOP CHECKING OUT!!!!! I HAVE TO CALL YOU BACK!!!!" Then they immediately drop you. You're left a bit flustered because their anxiety about dealing with this technology permeates through the phone. You are also a bit baffled by the behavior, as it makes very little sense.
1b) It slows down their conversation with the other person, as they have to squint at the phone whilst holding it 5 feet from their face, then try to find the flash button (on house phones, because they wouldn't figure out to press "Send" on the mobile to pick up the other call), then they have to frantically tell you they'll call you back, then they have to find flash again. This whole process can take at least 60 seconds, which, if you're sitting there as Phone Vic #1, seems like a really long time.
1b-1) It makes me feel slightly unimportant when my mom or MIL flashes over to me just to tell me they're on another call then drop me like a hot crack pipe...but that is a bit childish (egocentric) of me. Therefore it doesn't constitute a legitimate annoyance. Which is why I have it as a sub-sub bullet.
2) It's really annoying to others when you pull the "I'm in line at the bank/Stop&Shop I gotta call you back" bit. Like, for the cashier. Or the person behind you. Not only do you have an obnoxiously loud Christmas ring tone even though it's now February, and you talk way to fucking loud, but it's entirely bullshit to answer the phone when you have at least two people waiting for you to move your ass along. Your kid/husband/friend/God can fucking wait a second until you pay for your shit/make your withdrawal. If you've noticed, another thing that annoys me is creeping into this bullet point and engendering some real emotion: People who talk on the phone way to fucking loudly. Or people on the train who have boisterous conversations at 6:11 AM all the way from East Weymouth to South Effing Station. Or people who think their EXTRA LOUD Brittney ring tone makes them cool. SHUT THE FUCK UP. I keep my shit on vibrate for more reasons than it tickles my right hip.
3) They flash over to tell you "hold on one minute let me hang up on Kathy". Five minutes later they're still chatting away with Kathy from book club. If you hang up they call you back and ask why you hung up (um, maybe because I have better shit to do than wait around for you to talk to me and it's just as easy for you to call back when you're available?). Then they tell you you're impatient. And that you weren't raised that way. Growing up subjected that attitude is probably why I feel bad about myself when someone flashes over just to say they can't talk to me. See, it's not my fault I'm crazy.
If you're on the other line, stay there. Call me back. I'm not you and therefore not (too, too) psycho. If you don't pick up when I call I will not proceed to call you 15 times in the next 30 minutes and send 911 texts because I want to know Auntie Whosie's new address. You can call me back at your leisure, preferably within the next few hours because that seems polite. If it's really important and I need an immediate response I might leave a message, send a text, or call back in 10 minutes. That way you'll know I am desperate to ask if it's okay to swing by now, instead of later, because I realized I forgot something was scheduled later. I prefer to do a follow-up text because more often than not a person can discreetly shoot you a response via text. Then the issue's closed.
There. I feel a little better. It appears that the entire thing was a wash: three pos three neg.
Pic via Windsor Public Library.