The main story with Will and Grace catching up with Vince and Nadine is a good one. Nadine (played to perfection by Kristin Davis) appears to be a better version of Grace - but then the cracks start to show and she is jealous of Will. Grace explains to her that Vince is gay - and the ending with Nadine running after somebody else is great. If only Grace had done the same things ages ago - she would probably have been a mentally stabler person!
The other storyline is a familiar one - with Karen pushing her way into Jack's career. This has happened before (when Jack was a magician) - but the ending with Karen going back to work with Grace like nothing happened is funny.