I just switched from Windows XP to Mac by buying a Mac Mini and I'm happy! It's been a bit of a struggle (IE: I'm currently visiting the forums to try and figure how to get the Photoshop CS2 Tryout unistalled properly) but ultimately, I've really enjoyed it.
So far, the biggest challenge has been getting used to command + z,x,c,v for cut,undo,copy,paste as the command key is in a different place than the windows alt key.
Another thing was I ran out of USB ports pretty fast. That's were the bluetooth comes in though. I'm waiting until I can afford a blue tooth keyboard and mouse. Hardware is a bit pricey for Mac.
As for power I've had no problems yet. I've had photoshop, flash, entourage, safari and itunes all going at the same time with no problems.
It's so quiet too! Of course when the fan kicks in it gets a bit louder but it's way more quite then my PC was.
As far as a guy that went from PC (Windows for years) to a Mac, it was a nice transition and aside from a few episodes of separation anxiety where I've thought, "Oh crap! What have I done?!?!" I'm really happy!