I can't comment on Skype, as I don't use it. I noticed a massive performance difference compared to my SF, but don't know how much of an improvement the SF2 was over its predecessor so I can't compare with that. Far less lag than my SF running Moldova MHMP overclocked to 729Mhz. Much snappier. Screen much easier to read and type on too.
Common problems? Several of us have a recurring blob on the screen which appears to be a hardware issue caused by something pressing from behind. It is not clear how widespread this is. Several others have reported random wipes/factory resets. A few others have reported a problem with the custom unlock screen, although this is easily disabled. I can't recall but those last two may be linked. Early units had a problem with a quiet speaker, but this has been fixed with an official update applied via a menu under 'settings'.
Out of the box, the G300 is a little disappointing, but the easy software updates make it a joy to use. It is a peerless device at this price point. A fully-functional ICS version is now available too, although the anticipated official version has not yet been released.