Vic,
Here's a few items - although not sure if they are delivered by Blue Pumpkin or Aspect;
ROUTING: As you say, routing can be factored by WfM. However (the down side) this does not work in unison with other, complex rules that may be within a standard routing strategy (Business Rules, timeouts, overflows, etc.). With the WfM-based routing, it appears to be "all or nothing", unless you are prepared to re-write it, from the beginning.
INTEGRATION: I would say that integration is a good one; WfM takes the basis of Agent details from CME, with the "bells" being that you add supplemental information for WfM to pre-defined Users on the system. This saves a lot of time if you are adding (deleting or amending) large volumes of Users.
ALGORITHYM: Arguable, but the Erlang-c(+) calculations placed on Scheduling and Forecasting works very well for larger volumes and with a large amount of historical volume (1 year +). Again, the downside is that if you only have a few staff in one Team (less than 5) or little or no historical volume, it doesn't perform too good at all.
VERSATILITY: There are many, many *many* ways in which to apply Forecasting. Take your own historical volumes, use 6 months, use all available, etc. Then you can update the interim results determined by the WfM engines, shift things around, move Agents in and out, fiddle around with breaks, time off etc. and then Publish it. Very versatile in that respect. Not sure about the other Solutions but this can handle a lot of amending before accepting and publishing.
GENESYS: Well, errr... it's supported by Genesys... meaning upgrades are free...(!)
- On reflection, I'm not sure any of this can be considered "fun" but I've never considered WfM a fun subject!

Tony