The iPad does not fill the e-reader niche.  The screen is not as friendly to the eyes as E-Ink.  It is still a standard backlit LCD as far as I'm aware.  It's also too heavy for pure e-reader use.  An e-reader should be comfortable to hold in one hand while lying on one's back.
Finally, I may be wrong but I'm pretty sure you can't transfer PDFs from your desk top computer onto the iPad to read.  That kills any chance of it being qualified as a good e-reader.