I use a Cintiq 13HD, and there IS a learning curve, the mouse point doesn't quite line up with your pen in the way you'd expect (even when you tweak the calibration), so I wouldn't say it's exactly like drawing on paper. Closer, sure, but not exactly like it. It also still helps to have programs like MS5 where you can make your lines smoother.
I could've probably done okay with my old Intuos, however I have a very annoying case of nearsightedness that made using the Intuos a pain. With my glasses off, I either hurt my neck leaning towards the monitor from it being so blurry and trying to focus, or had to put the monitor right in my face, which just....wasn't good for me, and I still found myself leaning sometimes...and with my glasses on, I got headaches and dizziness because even with the monitor pushed back a bit it wasn't good for my eyes, my glasses are too strong for that I think.
The Cintiq puts things right in my face like paper, which makes things easier. Now I don't have to try to focus so hard with a regular monitor.
I kind of feel like I'm the only one who ever had this problem with tablets. XD If I'm ever forced to go back to the Intuos, it....won't be fun. I might have to find a cheaper Cintiq alternative, even if it isn't perfect, because the Intuos is just too rough on me.
Though I've rarely had lag, sometimes the tablet will suddenly stop working properly, when that happens, I use this method to fix it without rebooting or whatever. Seems to do the trick every time without messing with my settings. -
http://fox-orian.tumblr.com/post/39456072610
NOTE THOUGH: DO NOT TRY THE BOTTOM 'PERMANENT FIX' SUGGESTION! BAD, VERY BAD!
I also had issues with the calibration suddenly going wonky in the beginning, but I haven't had that happen so much lately. Maybe later drivers fixed that issue...