I am writing this to help clear up a lot of misinformation that's going around regarding exactly what changed and how this affects the scene going forward.

The system update 11.0.0-33 was released for both New and Old 3DS devices on May 9, 2016 in all regions. The official changelog can be found here and a 3dbrew page with technical details can be found here.

Confirmed: arm9loaderhax users are safe to update SysNAND and EmuNAND / RedNAND.
Confirmed: EmuNAND/RedNAND users are safe to update their EmuNAND / RedNAND (but never SysNAND!).

Any user of the Guide (or Luma3DS + NTR firmware bin in general) will be completely unaffected by most of these changes since the NTR firmware bin replaces 11.0.0's firmware with a lower version firmware.

The Changes (or Lack Thereof)
Cubic Ninja [ninjhax]

• Lost access to both http:C and soc:U, which means Cubic Ninja on any version 11.0.0 and above will no longer be able to download it's payload off the internet. This means more code must be squeezed into the space of a single QR code, but smea believes this is only a temporary problem and can be worked around given time
• Received codebin physical-memory randomization which was originally added for the eShop in 10.4.0-29, which temporarily makes launching the exploit very unreliable until an update is released

Ocarina Of Time 3D [oot3dhax]

• Received codebin physical-memory randomization which was originally added for the eShop in 10.4.0-29, which temporarily makes launching the exploit very unreliable until an update is released

Pokémon Super Mystery Dungeon [supermysterychunkhax]

• Nothing

VVVVVV [(v*)hax]

• Nothing

Super Smash Bros. [smashbroshax]

• Nothing

friends-sysmodule

• fpdver was incremented once again, which means that once a server-side toggle is flipped (usually around a week after release of updates), users with outdated friends-sysmodules will be unable to play online

svcBackdoor11

• This function, which is used for many arm11 kernel applications such as BootNTR and RetroArch, was completely removed. This will temporarily break applications that use it unless you are running the latest Luma3DS commit

"svchax" (aka memchunkhax2.1)

• This was not truly patched once and for all, but has had some complications introduced
• New security checks in kernel heaps were added which makes "svchax" require extremely precise timing and trickery to execute, breaking it (possibly permanently) unless a fix is implemented
• Downgrading in general, regardless of any arm11 kernel exploits (like svchax) released in the future, has been broken (possibly permanently). The firmware now contains a hardcoded list of minimum versions, and will not let us install a system title of a lower version than in the list, even if we have permission to install our own titles. This will make downgrading on 11.0.0's firmware impossible if no software workaround is found.
  
• Currently, there is a hardmod workaround to flash an older firm to NAND and re-enable downgrading, but this could possibly be fixed in 11.1.0 and it's only fortunate that it hasn't been fixed yet.