GrafX2 is great IME. You can use Photoshop or GIMP for pixel art, but IMO these are best relegated to very particular kinds of operations. Using a dedicated pixelart app for most of your pixelart stuff saves time setting up and avoids showing options that are ultimately pretty irrelevant to pixel art -- of which there are many. Some features -- like tile autocompletion -- are only found in pixel-art specific apps.
A tablet is worth it for pixel art, but I recommend also experimenting with non-pixel-art (eg CG or ink, with MyPaint, Krita, or Photoshop) -- tablets are very versatile, building up your skills in other areas will help your pixelart skills, and experimenting is VASTLY quicker with a tablet than basically anything else I've ever tried.
I don't know what the recent Intuos are like. I recall finding my previous Graphire to be very slippery and challenging to control, and upon switching to my current Monoprice tablet, I was much more comfortable with the level of friction imparted (I would characterize it as 'drawing on a whiteboard' versus the Graphire's 'skating on glass'). In any case, all tablets I know of have relatively low friction levels, so it's quite different from drawing on paper.
Pen tip also is a factor in inertia, and I understand that you get a few different tips with modern Intuos packages, so you may want to experiment there. Naturally, the more friction, the quicker the tip wears down; but you may find this useful to ease into developing the finer control you will need to draw using a more frictionless tip.