Regarding NS2, graphics are sweet, but I do not like the gameplay changes coming from NS1. I literally thought NS1 was perfect, and NS:Source would have sold like hotcakes.
That being said, I did happen to stumble across NS2 Classic (http://ns2cmodpreview.com/), and was very intrigued. Search for "Classic" in the NS2 server browser and just connect to play it. I found one with just 3 people on it, so not much gameplay was to be had.
Long story short, it was everything it was advertised to be - it felt JUST like NS1, with additions where needed. There was even a ported NS1 map we were playing on (I think it was ns_eclipse), although the textures weren't done. It still needs lots of polish to be done, but man, is it promising.
Very promising though if NS2 classic takes off, and I think (hope) it will see more adoption as the NS1 crew starts to move out of HL1... And as more people in NS2 discover the wonders of NS2 Classic.