I made the jump from IE to Firefox as soon as I was told about it and I have never regretted it for a moment. The experience was faster, slicker, more accurate and altogether more enjoyable. This was when tabbed browsing had just been introduced and so that was welcome as well.
Over the years Firefox has grown up. As the market share continues to increase more and more developers are bringing out really cool and useful tools and plugins that make Firefox very powerful, especially for the web designer/developer. I would actually go so far as to say Firefox is now an essential part of my workflow as a designer.
Tools such as Firebug for HTML/CSS debugging, Colorzilla for grabbing a particular colour off screen, and SearchStatus for SEO information are just 3 examples of tools that I would really struggle to do without.
It is not all good news though. The more advanced Firefox has got the more problems it seems to have, especially on the Mac platform. It seems to have got progressively more sluggish and often consumes complete cores of CPU for no apparent reason (albeit more often than not it is Flash related). Stability is not what it used to be, and while all this is going on the competition are reigning it in and in certain areas overtaking it.
Unfortunately Firefox seems to have cornered the market in terms of plugins in the same way IE forced itself in the market based on being bundled with the most popular Operating System in the world. I say unfortunately because we are now in a situation where one of the best browsers available has a lot of people using it that have nowhere to go and no other alternative. This situation is never good for the end user.
The ideal situation is either one of the other smaller competitors will introduce a versatile plugin system to rival Firefox’s offering, or someone new will enter the fray with another, probably webkit based, browser which will force Firefox to pull its finger out and tidy up its core product.