Those read speeds are pretty similar to my Class 2 to be honest (I'd wager identical once you eliminate the variance introduced by the stopwatch timing) and the write speed I observed (6.4Mb/s) is significantly better than the Class 4 card.

All in all, I'm very happy with a cheap Class 2 device in my N800 thanks euchprof - but feel free to blow your cash on a Class 4 if you think it justified! I certainly don't think it is - the only benefit of Class 4 over Class 2 is when using the card in a PC card reader and performing bulk transfers where you should see improved write performance.