I am a happy T1 owner, and think it's great. I bought mine back in Oct 2011, but if I were looking at buying one now I would seriously consider the Kobo for the following reasons:
1) Price at £79 it's a good price, though it can be picked up for £58.99 from
www.staples.co.uk (with a free toaster... random but true!!) Making it less than half the cost of the T1 in the UK! (T1 is still £129.99 here)
2) Firmware support/Updates - Kobo is actively being developed, whereas the Sony has had some bug fix releases, but no new features - how hard could it be to add an option to change how often the screen refreshes?!)
3) PC/Mac software on Sony is absolutely awful.
4) Sony reader store was 6 months late in opening, has a poor selection of titles, and the most expensive prices (£7.14 for The Girl With the Dragon Tattoo for example!). I have used the Kobo bookstore and found it far better on general price, usability and discount codes!