I find Trail Boss to be very hit and miss. Sometimes it's amazing other times I get pressure issues with very low velocities or just terrible accuracy no matter what I do.
Trail Boss produces more pressure for any given velocity than conventional powders. That isn't an issue unless you're shooting an antique meant for black powder but it is a good thing to know when using it. You can get pressure signs at much reduced velocities from where you would normally encounter them.
It was also originally designed as a reduced velocity/cowboy load pistol powder. It just happens to work in most rifle cartridges (to varying effectiveness's).
Following the 80% volume rule that Hodgdon publishes I've gotten some real winners and some terrible results as well. The 80% rule in a .45-70 with cast bullets tends to produce bad results and published TB data for the .45-70 is often below the 80% capacity mark.
Many of my most accurate cast bullet loads for bottleneck rifle cartridges tend to use H4198 or IMR3031. I also get great results with SR-4759 but it's been discontinued so I'm sitting on my last few pounds hoping they decide to bring it back again (they discontinued and brought it back before; sometime in the 1980's). If I want to go really light I'll usually just use 10-15gr of pretty much any fast to medium speed shotgun powder.
I'm not saying TB is a bad powder, it isn't, it just isn't as universally awesome as some people tout it to be. I have some pretty great loads using TB in some rifle cartridges. My Martini-Enfield in .303B just loves light loads with TB and cast bullets. As does my Swede rolling block in 8x58RD.