My only concerns to date have strangely echoed Pete's.
* I wanted the original knob
* I wanted the original boot
* I wanted the original hand-throttle
I heard the first-gen could handle most of those tasks with the exception of the boot.
Regarding the others weighing in on the Weltmeister and the Rennshifter. I think every camp seems to have consistent and valid points herein:
1. Most of the time, poor shifting characteristics can be improved upon with a new set of bushings.
1a. We don't have the worlds best shift linkage... it can be a challenge to build a mid-engine car in that era with a great shifter.
2. A Weltmeister short shift can help but frankly a 901 tail or side-shifter is a learned process.
3. A Rennshifter is an outstanding improvement.
4. A Rennshifter with the linkage adds another level to #3
5. A Rennshifter can be pricey, especially when viewed as "1/2 a Thousand" We all know there are varying levels of income or just plain levels of acceptance. There is a point where $500 can be too much or simply "cheap" when you compare it to a missed shift on a $12,000 race motor. I guess what I'm trying to say is, even the CSOB's may find the money for a Rennshifter and even the "Money's no Object" crowd may see it as 1/2 a grand in a car that cost them $2-4k.
My six was owned by a little old lady who went back and forth to work in it on sunny days (I kid you not). The bushings in that car crumbled under my watch. When I replaced them I had one of the nicest shifting 914's I've ever had (please read 1a). Remember, the six was still a tail-shifter.
I think a Rennshifter is a worthy investment. It's on my list of things to buy along with the linkage. I just need to find time to work on my car vs. everyone else’s!