Thanks for all the feedback, I went ahead with the purchase (hey, it's only $12 right?) but initial impressions are that while it will no doubt be useful once I've reached the top of the learning curve, it doesn't have the jump-in-and-play feel that Construct2 offers.
Megabeard, I've used Clickteam stuff on and off for years (since Klik and Play, and The Games Factory) which is maybe why Construct2 seems like such a familiar piece of software.
GMS will be one of those 'when I get around to it' applications I'm guessing, but no harm in having it in the meantime, just in case.
On the whole I'm pretty happy with Construct2 and am eagerly awaiting the Mac port of Construct3 when it sees the light of day.