I have the smaller one, I do subscribe to one journal but it is text based so
looks like any book on the kindle. If you get anything with lots of picture
content you might be disappointed. If you go to Amazon.com, then to the Kindle
store and look for any periodicals you might subscribe to (or might) and look at
the reviews. Most people are very honest and you will get an indication of the
limitations. Yes, there is a built-in dictionary which will give the definition
of any highlighted word at the bottom of the screen, clicking it will give you
more and the option to go to wikipedia for more information. The kindle does
have a basic web browser which looks good on wikipedia, but a bit weird on
graphics heavy sites. Amazon also regularly updated the dictionary, had an
update just last month.

Love the fetch function on Calibre, it is like building your own personalised
magazines. Like I said, PDF's are the problem, I think the DX (the larger
Kindle) would handle them better with the larger screen. I hold out hope that
Amazon and Adobe will come up with something or if someone will come up with
something.

I know Best Buy in the USA has virtually every decent ereader on display to play
with so you can compare your sony's, amazon's, nook's (and more) side-by-side. I
will hold onto mine until the colour e-ink looks like a worthwhile investment
(cheap and looks good).