"Set original tempo" for audio clips
Whenever an audio file without tempo data is imported into Reason, it assumes that the tempo of that file is the current song tempo. If for example the song tempo is 130bpm and I want to import a vocal that's originally at 125bpm, I first need to set 125 as the song tempo, then import the vocal and then change the song tempo back to 130 so the vocal is stretched correctly.
Having some kind of a "set original tempo" option in the context menu of each audio clip where one could input the bpm manually would fix this. Just import the audio file, then set its original tempo to whatever (125 in this example case), and Reason would stretch that audio clip according to the song tempo. Selecting multiple audio clips and entering a tempo would obviously set their original tempo to that same given value.
This was one small feature that I missed in Record 1.0 when I first tried it. I was a bit disappointed when it still wasn't present in Reason 6.