My experience of sketching on digital device started when Apple released Newton in 1994. Black & white. Bitmapped & pixelated stroke. Low resolution screen up to 320 x 240 pixels. But it was awesome! Finally I could sketch, archive it, share it through email, whenever wherever I want.
I was using the best painting software NewtPaint. I could send & receive file between Newton & Mac with desktop software. Good for archiving & printing. The screen was okay, 1 bit 320 x 240 pixels.
After Newton, I met Psion Series 5 in 1997 with built in Sketch app. 4 bit with 16 grey levels, 480 x 640 pixels. It was like, "Whoa this is it! The best sketching device!" But I hate its form factor. Series 5 was intended for business market, with folded screen & keyboard. Felt uncomfortable when drawing with palm of my hand rested on keyboard.
Then in 2000 I got second Palm device, Palm IIIx - the first was US Robotics PalmPilot - with 2 bit grey levels but smaller screen: 160 x 160. Though it was smaller with my previous 'sketching device', I love its form factor. Size wise, it fitted in my palm & my pocket. TealPaint software was my favorite sketching software, from year to year, device to device until Sony Clie PEG-UX50 in 2006.
2007, Apple introduced iPhone without stylus. It was a big disappointment for me since finger painting is not my thingy. I'm a Apple user at heart, but I never use it as sketching device. Not even iPad. Yes, there are tons of drawing app & unofficial stylus' available for iOS devices, but still, something is missing.
2012, I got Samsung Galaxy Note from a drawing competition. When I first ticked the stylus on the screen, I was surprised it recognizes my stroke pressure. Pressure sensitive stylus just like Wacom devices! This is it! So far it's the best digital sketchbook that fits in my pocket! And I couldn't stop sketching & drawing with it ever since.
Now I'm waiting for a smaller & cheaper Cintiq. That will be perfect.