I've been finding it hard even with the improved search times ;) to find previous purchases that was done through OzBargain deals especially if that particular item has been published multiple time from different OzBargainers/Vendors.
I would love to see, and hope other users agree, to a "I Bought This" button somewhere on each deal page that allows your purchases to be listed, hyper linked, and be found somewhere in my account to easily track deals you've bought for future reference. It'll be sort of like a Wish List, but more of a permanent option.
OzBargain would also benefit from this statistically as well, it'll give out figures on how much users do actually buy, highest selling category, etc. Possibly maybe even a new badge cough dot.
It also benefits those who completely forget about purchases of smaller items that still add up, like bang good or DealExtreme.
This was discussed a few days ago in the Comments/Feedback/Suggestions thread here.