I got the Signature Edition since I was a huge fan of the first one (Despite the buggy combat and laggy graphics). It was worth it for sure, not least because of the BioWare humor in it.
The combat is epic but sometimes a little jumpy and sometimes a little too frequent (the "random encounters" from the first game are like all over the place here). The story feels much bigger and all in-all I really liked it the first time I played. I tried replaying it with a new character but it really kind of felt the same even though I tried to choose differently during all the key moments. It was more replay-able than the first one, though.
Importing a save from Origins was a bit disappointing. The developers bragged a whole lot about it but your choices don't really make much difference in the end.
But in the end it was totally worth it. The banter between companions really makes up for everything else