I suppose a difference of speed turns into a difference of ability at some point. If you can't rely on tail calls, you will have to manually trampoline the cal

I suppose a difference of speed turns into a difference of ability at some point. If you can't rely on tail calls, you will have to manually trampoline the calls, just in case the optimization didn't kick in and your program dies. Or like xmtp or mail or whatever, you generally write your client assuming you are going to talk to any spec compliment server, which can stop you from using some extensions if you aren't sure they will be supported. Possible is not the same as guaranteed.