Hmm, good idea. I suggest the "Hot deals" section for that.
Unless someone beats me to it, maybe the criteria can be the following:
Product manufacturer: (e.g. Gigabyte)
Company handling MIR: (e.g. 4myrebate)
Product:
Country MIR letter was sent to:
Amount of MIR: $...
Processing time: (X days / weeks / years / undefined)
Format of rebate: e.g. prepaid card, cheque
General satisfaction:
I only remember 1 MIR process that I did recently, so if someone else can suggest criteria before I decide to make a thread or one gets created... need to go to class in 9 minutes

It was one from Gigabyte that took around 4 months.
EDIT2: Maybe we can encompass all non-instant rebates, e.g. Staples online rebates that require you to fill out a form without actually mailing anything...