I have always said “If it aint broken then don’t try fixing it” or “Sometimes being on the cutting edge of technology only ends up being the bleeding edge of technology” and “Let everyone else find the bugs and only update when you have too and only when there is a x.x.3 or greater update”.
Due to new Apple-enforced code signature restrictions, applications like MenuMeters are not compatible with the OS X 10.11 “El Capitan”. Although the restriction is similar, this is not directly related to 10.11’s “System Integrity Protection” (SIP, aka “rootless”) feature and disabling SIP has no effect on MenuMeters.
Unless Apple makes the signature restriction optional, it is not clear that MenuMeters in its present form can ever be made compatible with OS X 10.11.
In the meantime I can only suggest that you do not install 10.11 if you wish to use MenuMeters.
Here is a list of other software either completely broken which could stop your machine from booting, does not work or seems laggy (runs slower than normal).
Adobe Bridge V5.0.2 (CS6) will no longer recognize some Cameras
Anything that requires Java 6
Brother Printer – Control Center
Capture One Pro 8 and earlier
Carbon Copy Cloner
EyeTV (performance issues when switching a channel)
Filemaker Pro 14
Final Cut Pro
Fitbit (no longer able to find the USB Dongle)
Firefox 38.5 (will not install)
Firefox 39b3 beta (will not install)
Flash CS6 does not work
Google Drive (it syncs data, but there is no icon on menu bar)
Google Chrome & Canary (Severe performance issues)
iWork ’09 (Pages, Numbers, Keynote) problems with the new pencil color picker (in 10.11.1)
LaCie Raid Manager
Logitech Control Center (Devices won’t pair)
Microsoft Remote Desktop (works for some)
Microsoft Outlook Preview 2016 (very buggy with exchange account)
Mincraft (java issues may need to launch via Terminal)
Movie Magic Budgeting
Private Internet Access
SyncMate (can stop boot)
SwitchResX (doesn’t work with custom resolutions)
VMWare Horizon Client
Virtual Box (can stop boot)
USB Known Issues
USB storage devices, including internal SD card readers, may become unavailable after system sleep and require either re-plug or restart to recover.
USB input devices may become non-functional on some Macs after several days.
USB 1.0, 1.1 and older 2.0 devices may not function.
Several minor bugs in Photoshop CC in 10.11
Parts of the text on the loading image are missing
Moving layers in the layers list does not display the line that shows where the layer will be placed
Holding the button any of the tools that open a subtool menu (for example, Lasso Tool/Polygonal Lasso/Magnetic Lasso) does not open that menu as it should, but only after you release the button