I'll start off by saying that I'm not suggesting you should not file bugs with Apple, you should. I'm also not going to suggest that Radar isn't a valuable tool to Apple, it is. But it's time to get something off my chest, something I've been wanting to rant about for ages.
I fucking hate Radar and everything related to filing bugs with Apple.
I cannot begin to explain how awful it is. First of all the radar software itself is a really dated web app. It's hard to find radars you've already filed and takes a lot of clicks to do anything useful at all. This alone really puts you off wanting to bother as it is so much effort to file even the most basic of radars.
Then you get the attitude of people at Apple. Most of the time they are absolutely fantastic and asking to file a bug is something I'm ok with. But the passive aggressive "Radar or GTFO" or "well have you filed a radar?" attitude gets incredibly annoying and off-putting.
And what about when you finally do file a radar? Well it's a black hole. Occasionally you will get a reply asking for more information. More often than not I've found it is for information you've already given in the original report. For about half of your radars they'll be marked as a duplicate. You don't know what the original radar contained, nor its status at any point. Your involvement is essentially over. And of course for the rest of your radars they'll just be left untouched.
So basically the majority of radars you file will end up being of no use to you solving any issues. You just file them and forget about them and maybe they'll be fixed (of course it's hard to know given Apple's release notes are often so piss poor in listing radars fixed). And it's a colossal pain to do it. And then people wonder why many don't file radars.
So what can Apple do to fix it? Well first off they could make the web app not suck. That would be a big improvement. The ideal thing though would be to let us file radars from within Xcode. Let us bring up a "new radar" panel with a keyboard shortcut and start typing. Let us save reports as drafts so we can start them when we think of them but finish them when we have time, which will stop the all too frequent occurrence of thinking you filed a radar that you didn't. Add a checkbox for including the current Xcode project and automatically attach a system profile for bug types that require it. Also let us dual post to Open Radar (though this isn't necessarily needed if other things are changed). All of this is in rdar://8749276
Next, Apple needs to open up Radar. They always use the excuse of "radars contain private information". Let me tell you, the majority of them don't. Almost every radar I've filed could easily be posted publicly without any problems for me, Apple or anyone. Privacy is an issue in some cases so Apple can just provide a checkbox to let us make sure a radar is open. Then they can then let us search these radars ourselves, which could save a lot of time if we could just file a "me too" rather than a lengthy report (rdar://10965656)
Actually reading radars would be useful as well. They do read most of them but sometimes they come back with incredibly stupid requests or dismiss any issue you have.
Finally, let us up vote radars. That way we don't have to file a "me too". If we can see a radar already filed that we have a problem with, we could simply up vote it as something important to us. And we could add our own comments to it and make it more a collaboration than lots of islands of secrecy. It would also reduce Apple's workload as they don't have to read and mark radars as duplicates. (rdar://10965728)
Most developers want to file bugs and get things fixed, but as it stands it is a colossal pain to do so, with little visible benefit, especially if the work to write a radar is large, and sometimes the attitude of Apple can completely dissuade you from wanting to bother. If I could change one thing about Apple's developer story it would be radar. Simplest thing I would do? Replace Radar with something like Stack Overflow.