The HTC flyer stylus uses an active digitizer which communicates with the tablet so the stylus can use a finer tip, and also the flyer has palm recognition so u can rest your palm on the tablet while writing.
The capacative styluses which will work with any capacative touchscreen such as iphone, android hone, tablet, ipad simply mimics the finger as input to the screen. These stylus are much cheaper and dont require battery, however these can not have fine tips bc the screen ony recognizes 6mm and bigger inputs. most styus u see will be around 8mm tips. also there is no palm recognition technology so u cant rest ur palm on the tablet.
I am currently using a rocketfish stylus from best buy on my transformer, its 16 dollars and for the price it is the best capacative stylus imo. i have used the targus and boxwave and they are just a bit short for my liking. Rocketfish also makes a stylus with a pen on one end and stylus on other which is like 22 bucks. Waccom, the active digitizer company also released a capacative stylus called the bamboo stylus which has a 6mm tip compared to 8mm that most companies sell, i havent used it but ive heard it is really good, but it is a bit priceier around 30 bucks.