I'm not certain what you mean by 'vibrant urbanism' exactly, but as a long-time Riverdalian, I'd say that the mix of Danforth/Gerrard/Queen, with Withrow Park providing the neighbourhood focus, was fabulous. The Beach, with all its summer craziness, would also be a pretty close match to Little Italy, say... although not during the winter.
My one cousin was a big Drake Hotel area fan, my other cousin bought a place in Riverside. Both were adamant their choice was THE hipster heaven. To each his own.
I feel like the parts of the East Side that have vibrant urbanism are still smaller than in the West Side though. The Beaches were pretty sleepy even when I was biking around there in mid September this year. Basically the area you're describing (West of Jones or so) is mostly the 19th century part of the East End and it is similar to the 19th century part of the West End in terms of vibrancy but not in terms of size. The 20th century streetcar suburbs of the East End are imo similar to those of the West End, which are much more expansive, and include St Clair West, High Park, South Etobicoke and you can even include the trolleybus suburbs of Eglinton West and Bloor/Royal York as having a similar feel.
You are seeing very intense gentrification happening in the East End now though. In terms of change in income between the 2006 census and 2011 National Household Survey, pretty much the whole east end has since significant gentrification, the Old Toronto part but also parts of Old East York and pushing into SW Scarborough.
The West End is more mixed, overall it is gentrifying but much of it at a more moderate pace, covering the areas south of Dundas up to Kipling (New Toronto excepted).
North Toronto hasn't really seen an increase in income in this time interval, I guess it's already gentrified, being the wealthiest part of the GTA, so it can't really go much higher.
You also seem to be seeing significant increases in income in a few areas further out, including Weston and some of the surrounding 40s/50s suburbia like Maple Leaf, and in the NE in St Andrews-Windfields, York Mills/DVP area and Wexford. Areas even further out aren't in uniform decline, although there are several areas, both in the 416 and 905 suburbs that have experienced declines in income.
Obviously when you look at income change at the census tract level, new construction will have an effect. For example there's a census tract in SE Oakville that includes part of the GO Station area, and there were 1-2 new condos built there, which I guess catered "merely" towards the middle/upper middle class bringing the census tract household income down even though the neighbourhood has otherwise been getting wealthier. On the other hand with the GTA fringe you might have a lot of big new homes built in census tracts that previously had more modest homes, but the incomes of the people living in the more modest homes didn't necessarily increase even though that of the census tract did.