Hey Moloko, see? The more you tell about your personal use of the current device, the more and better can these guys here help you out with the insight you need. I know how hard it is to let go of what felt like the perfect reader for years, especially after making excessive use of it's perfectly implemented particular functions all the time.
Calibre, footnotes, performance under heavy load, wikipedia access, accessibility and quality of dictionaries, ... and all that in direct comparison to the outdated device you know is capable of to your liking: Reviews normally don't cover it widely enough or at all. I don't have much to add except for a massive

to all the mobilereaders who tried and figure how you (or we) would use a device that's unknown to you (us). It's a big help for guys who need a new home for reading like we Sonyiacs do now!!
Thank you for stripping away the usual review blingbling, what's in the package, how is it packed, will the edges of the device hurt fingers made of jelly, is it fancier than others, is there a change in resolution that no one would see from usual reading distance but has to be hyped over real life reading anyways etc. Thanks for the focus
To answer the question about Kobo and dictionaries: While playing around at the store, I found it pretty much useless for e.g. conjugated verbs. Also, it showed blank for too many words that Kindle and Sony would find. The depth of explanation was also far below the Sony and its Collins'. Kobo is pretty much dead for me until they offer the chance to buy and implement real dictionaries from publishers. Kindle does that, but where I live I'd risk warranty void by jailbreaking a device (Paperwhite), which
- doesn't havw a brighter screen (brighter than your T1's though, definitely!) with the (for me) annoying, cold frontlight turned off and
- makes me loose the four buttons I really like on the T2,
in order to work right with the best ebook managemet tool in the world, calibre.
The conversion from Epub to AZW for Kindle wouldn't be a prob for most of my books, but I'm really not sure about history books and the truckload of footnotes, which come with those. I know how massive these footnotes can become, because my wife studied archival science (and works in that field for over a decade) and tossed alot onto her T1

To me it often seemed to carry more footnote than continuous text.
You should try and test that in a store with the most footnote-ridden books you can bring in. Or:
"Historians around? Anyone?"