Hi,
I switched over from Librie to Iliad. I already enjoy the reading experience on the iliad. Yes at the moment it takes about double the time to make a page turn on the iliad compared to the Sony. However iliad screen size and resolution holds easily double the amout of text compared to the smaller screen of the Sony. So altogether waiting time is close to equal.
If and when prerendering helps, the situation will even be better.
Another positive aspect, which looks very promising to me is the speed of further development so far and the activity around this device. Software upgrades seem not to be that common with other reading devices..