I never bothered switching to a new editor. I said, "I'm already used to Hammer, it doesn't matter."
Then I tried making a house like this:
When I finally got to a point where I needed to compile, huge gaps in the roof everywhere! Parts of the roof were distorted. It was a huge mess. All those off grid vertices killed it and since I don't usually make geometry that complicated I never had any major issues like that until now. So it lit the fire under my butt to download Sledge.
After setting up Sledge I recompiled, and it's now much better! Though, unfortunately, since I created the geometry in Hammer 3.5, it didn't fix it entirely, there are still two thin gaps in the ceiling including this one:
But I'll deal with that. Not enough people will play this map to be worth the time rebuilding the entire top of the house, the roof is not touching the void so it won't create leaks, and considering what an unsightly wreck it was before, that seam is nothing (that same seam looked wide enough to chuck a nade through when compiled in Hammer and every other brush seam was just as wide).
So all I can say is, thanks for your work on Sledge. I regret not listening to everyone on here and ditching Hammer sooner (only thing I miss are my 2D scrollbars but auto visgroups and a much improved texture browser more than make up for that).