The last six months or so I've been trying out a Lenoveo Thinkpad Tablet for sketching:

It's an Android Tablet and the main reason I got it is because it has a pressure-sensitive pen (256 levels). The pen is a so-called N-pen. It not being a Wacom is sort of irksome - for example the pen is not detected when the pen is lifted from the surface, and it requires a battery. But the tablet is pretty cheap and I've had a lot of fun with it - and even having just a little pressure sensitivity makes a BIG difference when drawing.

I've tried a slew of different painting applications (there are seemingly no major open-source painting apps available for Android?), but so far what I've been going for is the $4 Sketchbook Pro, which also seems to be what most sketchers use. It has layers and a nice array of brushes, which is pretty much all I require. There are other painter-ly apps available too and I have gotten a fair share of them to try (they are so cheap there is no reason not to test things in full versions).
For painting, it seems Infinite Painter might be the best bet - it has decent brushes and focuses on blurring and smudging well.
Storyboard Studio focuses on producing storyboards for movies or comics. It has a simple way to flip through pages and some basic but useful brushes to do it.
PS Touch is PhotoShop's venture into tablet space. It was quite a disappointment since it's really just intended for manipulating photos. You can apply some standard filters and do some basic manipulation. I got it for the select/crop tools but I find I just as easily export to the computer and do such things in GIMP - and Sketchbook has since gotten limited abilities to do this too.
Layer Paint Is a painter app that has, well layers. It's pretty fast to work with but I've not gotten into it very much, I didn't find the brushes all that appealing.
Pose Tool is actually very cool. It's a digital ley doll: You choose a gender and a few basic morphologies (like man/female, athletic/fat/slim etc), and then you get a 3D human model you can pose in any pose you want and look at from any angle. Very useful for studying anatomy and have as a reference for sketching. Unfortunately by tablet doesn't support having multiple windows open at the same time, so I cannot really use the Pose Tool for sketching reference on the tablet. It works fine to have it open next to the computer though.

I've found that it works quite well to do sketching on the tablet and then move onto the computer for final touchup in MyPaint/GIMP/Krita.

Tablet sketch (done using Sketchbook's mirror feature):

Final version (MyPaint+GIMP):


Tablet sketch:

Final version (I kept much of the sketchiness for this one):


Tablet sketch (I never developed this further):


Tablet sketch (done on the train):

Final version:


Tablet sketch:

Final version:


It's quite fun to work on the tablet. I notice I'm more keen to do small details when having direct pen-surface interaction than I am when working using a normal graphics tablet on the computer.
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Griatch

Interesting...
I've been wanting to try one of those sketching tablets for some time now. In what formats are you able to save the sketches to open in Gimp?

Hmm. Can I make a a guess about the Xmas card for next year?

The city scene is gorgeous... And it has this fairly consistent 2° lean to the left, exactly like the pictures I take with my camera. Makes it look even more like a photo:)

@Wallace

From Sketchbook Pro, you can output as PNG, JPG and PSP (the latter of which GIMP can read). You can also output directly to DeviantArt's Stash if that's more your thing. Personally I tend to just use PNG for transferring the sketch and then work from that. I generally have to up the resolution to 300DPI when importing too, since the tablet can't handle the 3500x2480 resolution I usually work in.

@ofnuts

Of course you may guess!

I hadn't noticed the tilt until you mentioned it, it may come from drawing righthanded and leaning over the tablet maybe.
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Griatch
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Griatch

I like the grey sketch as well and don't think you need to develop it further. They are all good

griatch: thanks for sharing your experiences! i like all the sketches too - i think troll girl is highly decorative in that sketch, like she would fit neatly in a printed logo or something.

Thanks for the info and the demo!

The grey cityscape sketch was a fun idea for a game screen I recall. Mostly an excuse to test different brushes though.

@AnMal:
You think so? I would personally think she would make a pretty garish logo.
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Griatch