I recently purchased an ipad2 and I was in love with it, being my first ipad. I got the 32g wifi version because where I live you need to sign up for a 2nd data plan and I simply didnt need another monthly bill when i never came close to my 2G data for my iphone and rarely need to tether becaue there is wifi everywhere I go.
So.... I got my ipad 2 just before rumors of the new ipad release started circulating.... as a result I went back to the store I got it from and having a friend work there had them extend my return date for a month which would give me until after the speculated announcement date. When it was announced I went back and had it extended again for another month so I could keep it until the new one came out (and even for a while after incase they ran out of stock on release day).
I was able to get my new ipad on the release date and I exchanged it outright. So for me, it was a no brainer..... While I love the new display, thats pretty much as far as it goes for me and since new ipad cant be jailbroken yet I actually miss my ipad 2 a lot. I'm sure that will change in time.
With that being said if I could not have returned my ipad 2 and had to sell it for substancially less.... I probably wouldnt have bothered to get the 3.
If you are going with the two however, I would say just get it used. The resale value depreciated when the 3 came out making it a good time to buy it used for much less.
If you are set on buying new, go with the 3. Not only will the resale value be higher when you decide to get the new model when it comes out but you also have to keep in mind that as time goes on apps will be desiged for the 3... and the two will become old news sooner, just as the ipad1 did.