Tuan, I agree with most of your point. iPad can defintely be better .. and many of the problem can be addressed by some software modification.
However for your information, Apple does have an optional accessory that will allow us to read our SD card. "iPad Camera Connection Kit
The Camera Connection Kit gives you two ways to import photos and videos from a digital camera. The Camera Connector lets you import your photos and videos to iPad using the camera’s USB cable. Or you can use the SD Card Reader to import photos and videos directly from the camera’s SD card." (http://www.apple.com/ipad/specs/)
I am pretty said that the video outpout of iPad is not even 720P.