I'm still using the old RE because I have so little time to work on my route projects, and I already have a rhythm in place for working in 20-30 minute sprints. Everything I'm working on already has Demex and SRT Terrtex, so I don't see much of a benefit in changing.
If I were working on a brand new route, I'd be more willing to invest the time in starting it in TSRE from the beginning.
The other issue is what I'd say is a lack of consistency in the commands. If there was a quick reference chart that had the equivalent MSTS commands listed side by side with the TSRE way of doing it, I'd be more willing to try it. I'm not going to wade thru literally hundreds of pages of forum posts here or on ET to do the conversions on a one by one basis.
Again, I've got 20-30 minutes here and there, much of it without internet connectivity, and 10 years of finger memory where I don't have to even think about what I have to do to perform a particular task. You can't downplay the usability challenges involved with learning a new tool. ORTS put a lot of thought into keeping certain keystroke commands the same, mainly for that reason.