I plan on getting the D3 shortly after release for a number of reasons.
-4G is not a problem for me, as I have a 4G LTE mobile hotspot and my city will be getting 4G LTE turn on July 21. If I need LTE, I can just turn on the hotspot. I also hear that cities that have 4G LTE turned on are getting faster 3G speeds thanks to the increased bandwidth.
-I have to have a physical keyboard. Some people have no problem speed typing on a virtual keyboard but my thumbs and index finger begin to turn red after constantly tapping on glass. Also, when you are using a virtual keyboard in portrait mode, which I use like 50% of the time, the onscreen keyboard takes up like 90% of the screen leaving you no room the see auto-corrections, suggestions, etc., and if you move to another field using the onscreen keyboard you have no way of knowing what field that you'd be typing in unless you minimize the onscreen keyboard or switch to landscape, then you would have to tap on the field to get the onscreen keyboard to come up again. That's too much work for a text/forum/Facebook/email freak like myself.
-The 512 MB of RAM shouldn't be a deal breaker seeing that the D3 is shipping with Gingerbread which does a good job on memory management. The D3 should get Ice Cream Sandwich, which will do a better job than Gingerbread on memory management, by March of next year.
Edit:
-Battery Life is important. The Droid 3 Should have decent battery life as compared to it's 4G LTE-enabled brother.