as a counter-side, i must say i bought both of my keyboards without playing them. and the E60 i bought before even i could read some serious reviews on the internet.
this is very risky, and alot of research is needed anyway, but once you hear the demos, you read the manual, read the forums and ask questions, i believe you get to "know" your future to be keyboard good enough.
when it comes about many choices, particular sounds, styles, really clear preferences and so on, i agree you better play the instrument before actually buy.
my point is there's not such a terrible thing to buy unseen. just assume the risk.