i dont think the ETREX will have software that will emulate the small screen on the unit on the laptop.
all (okay, with my 8 y/o garmin 12xl unit) gps units spits out data. only your GPS data. in garmin's case, it can spit out NMEA sentences or their own proprietary stream (which they finally released a few years ago). the software will just interpret the data and plot your current position onto a map that the software has...
i can tell you this, and since i've had my 12xl, i have searched high and low for the best software to use on a laptop.
and right now, microsoft streets and trips (S&T) is the one i constantly load on my laptop.
there was one year, where i bought every single software i can find. i had the NG topo map one where it uses scanned USGS maps. i didnt like that messy look.
i've had the past 2 version of DELORME's TOPO DVD software. i like them for the topo use. like S&T, the maps are rendered and can have very good street level features, but i dont like how the maps are drawn.
only downside of S&T is that i wished it looked like this view:
REMEMBER, this is NOT an actual product.. just a wishlist that people have sent to MS...