The best answer to that question is that it depends on where you live, and what kind of paddle you’re looking for.
For those of us who live close by (in Elora, Fergus, Guelph, K-W, etc) the river is great. It’s just outside our door and we paddle all season. Summer low flows of ~5cms in the Gorge can be a bit bumpy, but it’s still water nonetheless.
With the rain, the water has come up marginally from 5 to 7cms, which doesn’t really change the character of the river, but reduces the scraping through some of the shallowest sections.
To get to answering your question, though:
5 or so cms (summer flows) is good for people keen to get wet who don’t want a long drive, and is also a comfortable flow for novice paddlers. It is not great if you’re looking for a big wave to throw tricks on. If you’re looking for big waves to throw tricks on, head somewhere else.
If you’re interested in running the Gorge, but don’t want the scrapes of some shallow areas, look for flows >15cms. We won’t see that until there is lots of rain. We had lots of rain the past 36 or so hours, but the GRCA simply allowed their reservoir to fill. The online summary isn’t super precise, but it looks like the Shand reservoir is now full … so, if there is more rain over the weekend, they may open the Shand Dam, which would mean decent flows through the Elora Gorge.
Hope that helps.