The sony doesn't allow you to make notes or mark/delete stuff you've read.
I own a 505 and have never actually registered with the Sony site because it doesn't seem worth the effort for a non-US buyer. I mostly buy from
www.fictionwise.com with a few purchases from a couple of other sites and a lot of free downloads. For travelling that might not work so well, but I use calibre to grab a few newspapers and blogs every morning and dump those onto the device.
For travelling the only hassle I found was getting access to USB power to recharge the thing. Buy one of the power cables for the Sony portable game thing, it's just a Y cable with USB to miniUSB + power so you can use the 505 while it's charging (and it charges noticeably faster). Means you need about 30 minutes a week to charge it.
Aside from that I fill it up with books and magazines before I leave home then just read through them while I'm gone. I carry a USB key with the calibre installer on it in case I find internet access and want to load up news and stuff.