I would definitely never go back to a rubber dome keyboard.
If you're serious about looking in to one, make sure you read up on the different switch types. Many of the complaints against mechanical keyboards made in this thread only relate to specific types of switches.
I use a Corsair K90 with Cherry reds at home since I'm mostly gaming, and since I play a lot of music games it's really become indispensable. At work I'm typing a lot so I use a KBT Pure with Cherry black switches (desk space is at a premium too!).
The number one advantage for mechanical over rubber for me is the key action - it's perfectly smooth and even every time. With a rubber dome keyboard it changes depending on how the rubber buckles, so sometimes it feels like the keys are unresponsive.
Don't get me wrong, switching from rubber to mechanical there will be a 'breaking-in' period where you will double-tap keys by accident or press two at the same time (especially if you're using softer switches) but they feel far superior to use once you're used to them. For me personally it was around 5 days to adjust. Similarly, when I moved to harder switches at work there was a period where I felt my fingers getting fatigued from the keys being harder to press.
To the people getting down on expensive peripherals I say this: 100% of the time you're actively using your computer you'll be using them, so they may as well be decent. They'll also last you a hell of a lot longer than any internal components you'll buy.
Going back to the original question - there's nothing good about 'gaming' keyboards, unless you're after something very specific like macro keys (of which you could use a software solution anyway); they're mostly a gimmick. The real question is mechanical vs. rubber dome. Likewise, a 'gaming' mechanical keyboard will come at a premium; whether it's worth it or not depends on what features you use.