Does anyone else use the Delay effect as a bpm calculator------- 
No, I use my Electribe which has tap tempo. Why would I use the Delay by the way?
Sometomes for a nice effect, i calculate the bpm in milliseconds using the delay effect(with the effect turned off). That msec value goes nicely in the flanger effect for instance. Any setting in renoise that can be set in milliseconds i play with temposynced values. Ive been able to get nice effects with compressors using this method, and it helps with reverrb to be able to set temposynced tails.
Interesting approach.
Yeah, have some fun with it. Whats an electribe by the way?
I often do so too 
Some sort of sampler/groovebox, a Korg Electribe-S MK2.
now that looks like alot o fun!!! I think i saw one in the cockpit of millenium falcon:-)