Truth is, if you use the Amazon ecosystem, then go with the Kindle - that is its biggest advantage. If you get books on the side, then it is a harder choice. Yes, Calibre works slightly better with the T1... but I don't see a big difference.
Some observations on less-discussed features:
1) For magazines and periodicals, the T1 is flawed. If you plan on subscribing, auto-delivery does not work - and that might tip the scales towards the KT. The KT has a 3g option, that could be useful in that context. I prefer the KT when it comes to periodicals and newspapers. It has more options as well, in that context.
2) If you are considering covers with lights, note that the KT cover has an intelligent design (powers form the device, no need for external batteries) but it is expensive and the positioning of the light can be very annoying when reading in bed (tends to 'shine in your eyes'). T1 wins the lighted cover battle.
3) Neither is great for annotations, but the T1 has a slight edge, given the stylus.
4) Lack of page-turn buttons can be an issue. I find that there are many instances where I would rather not touch the screen - and it becomes an issue with the KT.