Oddly enough, I got the exact opposite reaction to 1803. I have a i7,1TB,16GB configuration with both the "System Protection" & BitLocker enabled. After the initial 1803 update my machine kept crashing / locking up, so I reloaded it deleting all partitions and started new. I partitioned my hard drive at a 60/40 split and BAM! - My machine is running super fast - It felt like some sort of 'break-in' period had ended and things started ticking, thus running like I would expect a 4.2GHz processor to perform. Yayyy