NRF51822 PCB layout review

Question

Hello, a few days ago I was having trouble with RF performance on a custom PCB using the NRF51822. I posted here to get feedback and figure out where the design went wrong. 
 I've since then re-designed the board, taking into account the faults of the previous design. Could someone review this design for any obvious mistakes / design errors before I send it off for manufacture? 
 Relevant part of schematic: 
 
 PCB top: 
 
 PCB bottom: 
 
 Main changes since last time: 
 
 Use integrated balun instead of discrete matching network 
 Antenna on same side of PCB as SoC and matching network 
 More free antenna placement 
 RF and SoC grounding prioritized 
 Four layers (Bottom components and signals - ground plane - power traces - top components and signals)

Einar Thorsrud · Accepted Answer

This seems much better than the initial board. I have few comments, though: 
 
 You should have a pi-network to tune the antenna, as it is always required in practice in order to get good performance (regardless of what the antenna manufacturer claims). In order to make room for it you probably need to move some components. 
 In general it is a good idea to use all empty space for ground, so I would put ground copper on the power layer as well. 
 I have not compared the placement of your balun to the reference design in detail, but from looking at your layout it seems OK. If you have not done so you should measure trace lengths etc., as it is important to exactly copy the placement of the balun relative to the nRF.

NRF51822 PCB layout review

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