1. Chrome is fastest on a slow computer, but will slow it down if you're not running a multi-core processor. If your computer has no issues, Firefox, IE, and Chrome are all equally as fast. Yes, really.
2. Firefox IS open-source. Whoever said that is correct, and you explained it well, too. Like Linux, anyone can mod and/or improve the program, and the developers will probably update it it with your additions, and credit your name.
3. Whoever said something about the bugs is correct, too. But it really doesn't matter if you have a faster computer, like I just said. And they aren't getting fixed mostly because... well, most programmers tend to be extremely lazy. It's kind of funny to watch them, actually. Not so fun to be one.
There is a thread on browsers, actually. Possibly in the Hobbies thread? Not sure, but unless either the OP or the other inquirer need additional help, this thread should be resolved.