This is a big year. Both IE and Firefox will release new versions this year. That hasn't happened ... ever? IE8 had its first beta, whereas Firefox 3 is at beta four. Indeed FF3 is much more polished at this point than IE8. However, I must say that Microsoft has been smarter than the Firefox team in a number of ways.
First, IE8 includes an improved IE Developer Toolbar by default. The IE DevBar is roughly equivalent to Firebug, but Firebug does not work with FF3. Of course you can’t really blame this on FF, but IE8 is much more web developer friendly. Web developers are the primary (only?) audience for beta browsers. IE8 also includes the IE7 emulation mode. Again this is very nice for web developers who have to program for IE7 currently, but need to get a head start on IE8 (wait, isn’t that all web developers?)