509/510 have problems like being grossly undersized with the single LRV, and the issue inherent with running a segregated ROW in a truly urban environment. Lots of traffic lights, lots of stops, slower avg speeds. But that's inherent to its environment. Put an SELRT or FWLRT in the same location you'd get the same result.
On the whole though it's got grade-separations going into the subway (on each the 509, 510, and 512), and high frequencies. Those are big bonuses. Not on the scale of grandness as Crosstown, but I still consider them and future Waterfront LRT to be LRTs.