It's strange, some players have a better time of it up here, while others do well in the SH and are pretty mediocre up north. Rico Gear, CJ Van Der Linde and Owen Finnegan come straight to mind as flops while the likes of Brock James and Paul Warwick were far better up here than they were down south. Sonny Bill Williams wasn't great for Toulon but is fantastic for the All Blacks. Go figure.
As for SH players bringing attacking skills to the game in general up here, I'd say it's not had a major impact on playing style. The three best teams in Europe this year - Toulouse, Leinster and Northampton, all were made up predominately of NH players but played some fantastic rugby. A lot more is down to coaching. Speaking from a Leinster point of view, the likes of David Knox, Alan Gaffney and now Joe Schmidt all have done very good things for our player's skill sets. The influx of SH coaches had a far greater impact than the influx of SH players on playing style imo.