My advice, for what it's worth, is give it a bit of time to be 100% sure you can't live with the old one. I went through the must have something better phase as everyone probably does but found I adapted quite easily and then saved my self a fortune, mine's an NTG1 so bigger bucks/headaches involved.
I now do nearly all my driving using the directions in the instrument cluster now, the countdown is far more useful, much safer given the crap position of the COMAND screen, and miss this function in newer cars with supposedly better navs as Alfie hinted at. The limited postcode function isn't great but I found I started using the POIs more and most of the places I needed directions to were businesses, eg hotels etc, so easily found.
Yes, the graphics aren't great but i leave it on MAP when not using the nav which at least is a rainbow bedspread like a lot of current nav screens as it's handy for traffic at any time.
As Alfie also mentioned, I read loads of horror stories of these cheap (quality not so much price!) head units packing up quite early in their life though you might get one of the goods obviously.