I just got a v7 swap into my 04 WRX. I had a shop do it so I didn't actually do the work myself. I did get the JDM ecu and wiring harness so it was pretty straight forward and everything works, including the AVCS.
I would highly recommend the v7 if you're looking for a new motor. It surprised me the first time I pushed it hard and it really is very smooth.
Also make sure to get it tuned before pushing it. I get boost creep and had to upgrade the stock injectors and my fuel pump. Not sure if you will have to or not but getting it tuned will tell and better safe then sorry.