Tried the 1504 test build since yesterday, coming from the 0604 one. Didn't have WiFi problems, but at times it was extremely laggy. And with extremely I mean I had to wait >10 sec for some response, sometimes it took even that long that I thought it doesn't come back so I decided to reboot, which happened quite a few times.
Another thing was with the ring tones and notification sounds. It showed 2 ring tones named Argon (my standard ringtone), and the one that was used was a different from the usual one. In the 0604 build I have only one Argon, but it is the wrong one.
And for the alarm clock I always used Arcturus.ogg from /system/media/audio/notifications, but the sound that is played when the alarm goes off is actually a beep sound. However, when playing Arcturus.ogg with some media player, it is the expected tone. BTW this is the same in the 0604 build.
Now I'm back with at 0604, waiting for the next build.
BTW going back to 0604 wasn't all that trivial because TWRP couldn't find the CWM backup, so I first had to flash the 0604 zip and then restored the 0604 backup.