The Kindle Fire HD is a fantastic little tablet! Pretty dang user friendly, but the software edge goes to the iPad. I do like my Kindle HD better than the old ball and chains iPad though...
The only drawback to the Kindle Fire HD I have noticed was its charge time and for some reason when I try and watch youtube videos through the mobile site it won't let me. I have to go to the desktop version and pray it isn't flash embedded.
Ipad all the way. I have both. I won the kindle fire HD in december and bought an ipad shortly after. The kindle fire isnt bad but it just doesnt compare. Its slower. It comes with lock screen advertising unless you opt out by paying $$ (not a lot but its just irritating). However, its nice but dangerous being constantly logged to amazon. I also find the layout/user interface of the kindle inferior to that of the ipad.
Also if you have an iphone, you can use icloud between all devices.
But, I would take an iPad or iPad mini over a kindle (or any android tablet) every time. I have had a Kindle Fire, a Galaxy Tab, and a Nexus. I always go back to my iPad.
My wife gave me Kindle fire HD for christmas. Its ok, but I don't like the virtual keyboards on any of them. I type too much. and don't like the one finger hunt and peck method.