This has probably been mentioned a 100 times
but if it hasnt,
reason could really do with some VSTi support,
the reason i say this is because i really like the powerful control you can have on reason instruments and over the arangement view
but recently ive had to use ableton to make those synth/bass/whatever riffs and then render them as wav files back to reason , this makes it a slow process when you want to change the key of even one note in a loop for a different part of a song since you have to create a whole new wav file, and you still wont know if that key change fits with the song
i only have reason 2.5

so slap me if its available in reason 3 lol