I have the same problem. This is a major issue in my opinion. I will try to outline two subsets of the major issue: first subset being how incoming calls are handled, second subset being how the manage calls button works.
When on call A, and call B comes in, there are three possible things to do: 1. ignore call B, 2. answer call B and leave call A active on the other line, or 3. hang up on call A and take call B. I owned a BlackBerry before my Droid, and when a second call came in, those three options were presented on a menu. On the Droid, you only have options 1 and 2. Which is a real problem.
For example: If I am leaving a message for person A, into their voicemail, and then person B calls, if I accept person B, then the call into the voicemail of person A is still active, just dumping silence into the message I was leaving. Or -- and this happens a lot -- if I am checking my messages, and while doing that get an incoming call, there is no way to hang up and leave my own voice mail and take the new call. The call into my voice mail is still active, and messages keep playing, and later when I call to check messages, it will be as if I listened to what was being played back.
The solution it seems you are proposing is to use "manage calls" to go back and hang up on person A after taking the call from person B. Doesn't that seem really silly? "Hi Steve, hang on while I go hang up on Bob, who I was talking to when you called." What if I don't want Steve and Bob to know who I am talking to, or what if it's a really important call with Steve and I can't afford to put him on hold to go back and hang up the first call from Bob?
Furthermore, the manage calls button is entirely devoid of any user feedback letting me know that a call swap has happened or letting me know which call is now active. Nothing on the screen changes, the call timer does not change, the caller ID does not change, there is no audible feedback or visual feedback. And, as has been pointed out on this thread, if one of the calls drops on its own, the manage calls button still stays there. You say that's not a major issue, but I strongly disagree. Because that is the *only* indication I have of whether that second person is still on the line. And, even worse, if you hit the manage calls button and there is not in fact another call to jump to, then it hangs up on the call you're on.
I get a lot of overlapping calls in a day, and with my Droid I am now paranoid about hanging up on people or making them deal with the inconvenience while I fumble through a workaround on my phone. Second, I would rate any issue that affects the core functionality of the phone and making and receiving calls as pretty serious. This is after all, a phone, with a lot of internet and graphical features, and not a tablet computer that happens to have some phone features built in. It's a phone first and phone functions should get core attention.
The BlackBerry and the iPhone have elegant solutions to this problem, and the problem set is easily defined. Just seems like something that got totally overlooked.
It seems like a lot of the posts I read in the forum are from people who use the phone more casually and aren't in business situations where it's important to manage who goes into voice mail, who doesn't, and you can't just do things like "say bye and hang up" or expect the other party to end the call.
And, as was pointed out in this thread, this becomes a real problem when one of the calls is someone else's voice mail or when you're calling your own voice mail.
And even if the "swap calls" function is the supposed work around, there is no way to end one or other of two active calls. Ending one hangs up on them both, which is clearly broken.