Formaldehyde is something I'd stay away from anyway, even if it does the job somehow better I'd rather let my slides die in few weeks of fading than suffer cancer myself or any of my closebyes sometime in the future because of using it.
I'm sure we all like what we use and are used to using.
Tetenal is probably THE most used kit by DIY home type of developers so no wonder. It's simple and elegant kit no doubt, comes cheaper per-roll too. With this 3-bath Tetenal kit my local lab has done most of my slides and often I'm not satisfyed with the colour results when I knew I had the best possible colours spotmetered on the shooting scene.
I've always wanted to try the real thing: 6-bath as the process should be and was designed for, so hence the DIY experiment I'm undertaking now. There're no guarantees of course. But just couldn't miss it to try the real thing at least once in my life
This is how I'll do it, home-brew style.
Fuji E6 development kit by tsiklonaut, on Flickr