I'd been a Serato user for ages and the only problem(s) I found were the pain of manually moving all my crates and re-establishing my hot cues. Beat grids took a little bit of finessing on some tracks, but for the most part things were fine.
Remember; normal analysis for songs with consistent / electronic percussion, dynamic analysis for songs with a live drummer or varying percussion. I find this better than Serato because their software doesn't have a dynamic mode -- you need to manually adjust a grid for any songs with a wavering tempo, so already you're ahead of the game if the software can determine the type of song and how to grid it.
Personally, I just check 3 key points in tracks I know should be consistent; one at the start, one mid-way, one near the end. If you want to get accurate, enable the metronome and just flip through your tracks to hear if it's on-beat at those points. If you know the song may be a problem on dynamic analysis (eg. a disco track or track with a changing tempo), check the grid in a few points and adjust as needed.
There are some growing pains, but there certainly are more benefits to rekordbox than Serato DJ. Let me know if you need any more specific help