I'm opted into the coloured (colored for you antipodean folks) deal tags and wanted to offer some feedback on my experience of it so far. Specifically:
It would be good to be able to filter based on the deal stage. I thought a good use of the tags would be to identify inactive deals (the grey card background is a bit too subtle). However, deals earlier in the pipeline need a longer period before being tagged as inactive than deals closer to won/lost. It would be good to be able to specify if deal stage = X, tag as inactive after 30 days, where if deal stage =y, tags as inactive after 10 days.
It would also be helpful if the tag could appear on the deal itself, possibly under the main deal card in the left sidebar, as such: