Before BITOG, I was pretty much a devoted M1 user in my Tacoma. I tended to gravitate towards Valvoline conventional for everything else I had previously. For years, it was burned into my mind to avoid Pennzoil at all costs because of the infamous sludge myth. But, after doing some investigating and reading various threads here, I caved and tried Pennzoil Platinum in my Tacoma one spring about 2 years ago and fell in love. I liked the way the engine ran on it, sounded better, and oil consumption dropped. I've stayed pretty loyal to it ever since, although, I gave Amsoil a try about this time last year and noticed no big differences so switched back to Pennzoil and plan to stay there until something else comes along that works better for the same or better price.
I've always used Rotella products in my diesel, for several changes it was just the standard T 15W-40, but decided to give the T6 a try for better cold weather performance and love how much easier the engine turns over and starts now, even on a warm day you can tell it's not straining as hard to start like it did on the 15W. Rotella is cheap and easily found everywhere, I like using oil based on availability, especially considering my old 7.3 Powerstroke burns and leaks a little and needs makeup added throughout the OCI.
I started using Rotella T6 in my ATV as well and it seems to love the stuff. Although, due to concerns over shearing because having a shared crankcase and transmission, I'm going to give standard T 15W-40 a try in the quad this summer and see if it holds up better to shearing like many people here claim. The less gap in viscosities, the more shear stable as I understand it.
I'm really liking what SOPUS is doing, so I plan to stick with them until something else comes along that proves to suit my needs better. While other oils are really good, I'm one of those old school guys who doesn't like mixing different oils through the engine every OCI, even though it's not harming anything. Some habits just die hard! If I'm going to switch to something, I will either stick to it or dump it at my earliest convenience and go back to what I'm used to.