As much as I agree with the sentiments on both sides of this issue, I decided to participate in the upgrade offer and discovered that it was able to repair permissions on my El Capitan installation.....a function that wasn't offered by the version of Disk Utility that comes with El Cap.
I'm fairly certain that the long list of permissions requiring repair was the result of many years accumulated OS updates and not the result of anything recent....that legacy accumulation of potential issues is now resolved.
FWIW, there were no indications of issue or distress prior to running TTP8's permission repair function.
(So as far as I can tell, it could be very much like keeping a big stick near the front door to keep elephants out of the yard....haven't seen a single elephant since I started keeping the stick at the ready!!)
(edited to add the elephant analogy...)
I've actually always used Onyx to Repair Permissions. Yes, it is available in TechTool Pro, but when I perform my disk cleanup/maintenance/repair, and backup, tasks for each of my machines, the order of that is:
1. Use a Microsoft-provided "method" of permanently deleting EMails that I have deleted in Outlook (my EMail client) since my last maintenance (usually one week ago).
2. Run Onyx to Repair Permissions, and perform a number of its other, useful tasks.
3. Run TechTool Pro to perform a number of its useful tasks. That includes, in the following order: Memory Test, SMART Check, Video Memory, Fans Test, Sensors Test, (for my MacBook Air, Battery Check), Surface Scan (takes the longest of any task, but given my SSDs are only 256 gig, only about 25 minutes), Volume Rebuild, and File Optimization (I assume most folks know that Volume Optimization is both strongly advised against, and not necessary, for SSDs). I do all that, of course, from the eDrive partition TechTool Pro "makes" on each of my SSDs.
4. Run SuperDuper! to back up each machine to their applicable partition on each of my external drives (I have two of them).
All of that does not include any daily disk cleanup that I do on my own (exclusive of "deleting" EMails).
I actually have another program called "SMART Utility" that I run once in a while. I wonder which SMART "test" is more accurate. I just ran it, and for my 256 Samsung 840 Pro SSD inside my Mac Mini, it shows a CRC Error Count of 881. But, it also says: "Overall SMART Status: PASSED (in green)". TechTool Pro's SMART check shows error counts also, and in fact breaks them down into various categories. It also says PASSED for the SMART status.
For your "elephant" analogy, just last week Onyx came to the rescue with an issue I had booting my Mac Mini into Safe Mode (trying to go along with a request from another user). The OS could not resolve it all.
So, I am still going to be proactive in continuing to do what I have been doing, and using my "weapons" to keep
all monsters at bay, so to speak.
