Comparative DSLR viewfinder sizes
One of the significant drawbacks of the Four Thirds system is that the
smaller sensor (and imaging circle) contributes to a smaller viewfinder
image. The E1's high magnification and 100% coverage just enable it to
match lower-end APS-C sensor cameras.
(*) The 4:3 aspect ratio of the Olympus cameras makes their viewfinder
images bigger vertically. (Crop factors are calculated horizontally.)
There are considerable uncertainties in these calculations! The sensor
size "crops" aren't exactly 1.3, 1.5, or 2.0, and in fact notionally
identical sensor sizes vary between camera models. So I should really
recalculate these using actual effective sensor sizes. It's also worrying
that viewfinder coverages - with the exceptions of the 5D's 96% and the
E-300's 94% - only ever seem to be 95% or 100%...
Olympus E-300 and E-500 users might like to try out the AS-ME-1
eyecup magnifier, which provides 1.2x magnification.
And Nikon D100/D200 users have the option of a 1.17x DK-21M.