I use a 17mmTSE for my commercial architectural & interior work - mainly due to the lack of distortion it produces. I have used the TSE feature on a few occasions, but it was the lack of barrel distortion (there is a little but it's barely noticeable to an untrained eye) that blew me away, and sold me on it.

I also have a 90mmTSE - and I use that for the selective focus when shooting food and details. It produces some great shallow focus images, that add a little extra to a typical "still life" image for clients. It also makes for an interesting portrait lens too.