I have found a few bugs... er, undocumented features, but it may just be my phone. For example, I can't change CUSTOM to OFFICIAL: Custom just persists. Small things.
But this thing sips battery now. I took my phone off the charger at 4 AM, light to moderate use all day, it's 6 PM and I'm at about 50%. I can't speak to the Galaxy S5 tweaks, as I use Apex Pro Launcher and it looks the same as it ever did.
Getting Hyperdrive 8 onto the phone, however, was a sheer nightmare for me: I ended up having to Odin back to MJE, re-root, then ROM up to Hyperdrive KitKat. I nearly hard-bricked the phone by making a critical error when I was half asleep. What is the critical error? Make a note of this. Write it down. BURN it into your memory:
Once you are on Hyperdrive 8 and Safestrap 3.72 KitKat,
DO NOT REBOOT TO RECOVERY IN HYPERDRIVE! You know why? Because there isn't a custom recovery to reboot into. Safestrap is a recovery hybrid app; not the full-on thing. So as soon as I tapped that button (which you cannot remove, much to my dismay), the phone rebooted to nothing. Then tried it again. And again. Over and over and over. It was stuck in a seemingly perpetual bootloop from which there was no way out... not even with a battery pull.
Maybe it timed out after so many attempts... maybe it was my fervent prayers that did it
but she finally booted back normally and all is well.
So remember not to reboot Hyperdrive into Recovery! You've been warned! If you want to access Recovery, reboot normally and select Recovery in Safestrap. You also can only flash Hyperdrive in the STOCK SLOT: this is a beta release of Safestrap KitKat, and no other slots are supported. Once you have Safestrap 3.72 installed, make sure you also install Busybox.
All in all, happy to be on 4.4.2 but I find nothing here worth the effort or the risk to attain it. YMMV, of course, and others may crow about their experience. I look forward to their perspectives.