I thought I would mention this in case some of you haven't heard.  Garmin just released 1:24K Topo maps for WA and OR.  Unfortunately they are tied to an SD card so you can't load the mapset on all your devices, or even older devices that don't support the SD Media...

If I end up getting the Garmin Oregon I might go ahead and get this mapset as well.  It's about $86 at Amazon right now, retail is $99.  Also the Garmin Oregon is only $476 at Amazon as well.

Well this Christmas Santa brought me Garmin Nuvi 750. I diligently proceeded to acquire 24k map set for PNW. Although Garmin doesn't list this product as compatible I had good suspicion it is. Indeed works just fine. Only requirement is to deselect default map set in settings. Unlike I've heard of earlier models it is still fully capable of navigating to point of interest, feature etc with voice guidance, while displaying topo map with elevation profile etc.

Only limited downsides so far I found compared to Nuvi 500 and Garmin Oregon series are: 750 is unable to display shaded relief so one has to understand a little topo map reading and it doesn't have some features like compass (I prefer to carry a real one anyway), some silly geocaching game, there might be others I'm not aware of course, but I list them as nifty features rather than necessity.
On plus side 4.3" screen gives marginally better view of map for browsing. It seem to be pretty quick for rendering than scrolling in browse mode even with detailed elevation profile enabled.
Also 750 has capability to display tracklog so obviously it can be pretty useful to backtrack. I bet relief shading wouldn't be a big deal for Garmin to add but I doubt they can be persuaded to do so.

On side note I recently found this interesting info on  how to add contour lines to your default map set for Garmin units

Here are couple picks what it looks like on screen.

3D view with navigation - shaded releif or 3D would be nice. Should have zoomed out though.

True north view. I like it. Pretty usefull I would say.

Anyway should work on pretty much any Garmin

Yes I believe that's the intention. It copies just fine. I remember stumbling by 10 unlocks limit. You have to call Garmin and I guess you better have had registered that purchase with them.

Isnt this the same map set thats on the Nuvi 500 ?

so are these better maps for my 500