Drew is a standup comedian, and not an improv comedian (and yes, there's a difference - Greg Proops is the only one who could easily pull off both skill sets IMO). By his own admission Drew was a poor improvisor and the laughs he got were as much the audience laughing at him not being able to hold a character, versus the sorts of gags his co-stars got. He was included in a game at the end at the studio's request IIRC, as they wanted to capitalize on his name.
[Aside: After the DCS was done Drew actually started taking acting and improv lessons, and you could see in some of the Whose Line follow-up attempts that he had markedly improved as an improvisor. He always made a better host though IMO, and his success on TPIR is proof positive that this is where his groove is]
Anyway, I'm delighted that the show is back and with the original US cast, albeit a good decade-plus along. The show actually stopped filming in 2001, and ABC had enough in the can to show new episodes until 2007 (they even mistakenly included different cuts of the same games in some episodes!); they used every single game they had instead of just the best ones as the UK version did, and in the later seasons it showed. Having seen many of the show's cast in various improv-related stuff in the interm, it's easy to see that they still have it. I'm guessing that the guest of the week will include some younger talent thought to keep it fresh.
While I was always into theatre improvisation, it was Whose Line that really got me on the path to making it a second career. I currently manage almost 20 improvisors in three cities, and perform in two other groups as well. Despite this, most hardcore improvisors still look down on Whose Line as a form of cheap, go-for-the-laughs improvisation for the masses. Anyone who's been to a theatre improv show knows that Whose Line isn't as compatible with the more common forms of improvisation out there.
Still, for better or worse WL is responsible for popularizing improv for the TV-watching audiences at large; I do hope this new edition will bring the fire back.