I would deff go for it, 3 reasons;
1: Its an awesome Android experience phone like no other, yes the Nexus one has 2.3, but lakes the beautiful screen and the front facing camera, along with the Hummingbird processor, its just as smooth as butter.
2: Price, right now you can get it for as low as $49 a a new contract.
3: Updates.... the Nexus doesnt even have cut in line to be the first, heck it has its spot reserved for future updates...it can come late to the party and STILL have a first spot in line LOL- FYI to all those getting the next Evo 3D, Evo 4D, Droid X, Doid XX, Heck even the Galaxy Universe wont be able to do what a Nexus can do.
Now as far as it is worth now with the timing? That depends, yes the Next Nexus rumors will start coming late 3Q, but why does that matter? Lets suppose that the next Nexus will be dual core ( over hyped) or that the screen will be 4.5 ( too big for me).. What do you really want in a phone? Me personally great battery life, not too heavy, great speed....and overall just all blacked out sexiness.
Besides there will never be a "top" Nexus because there's always one around the corner, and we all know that this is just technology, period. I left the Evo for the Nexus due to the pure Android experience, heck I even rooted my Evo to have Gingerbread running on it! BUT I can confirm that its not the same expericnce, the Nexus IS what rooting is trying to be.IMO