As an international customer, Impulse is one of the worst services going. It's as if they go out of their way to be as useless as possible unless you are in North America. For example, they insist on charging in USD, but by default will show you a price in your local currency. Doesn't sound like a problem, until you realise that the rate they show you can be significantly lower than that used by your credit card/Paypal.
They then make the process of viewing the USD price far more annoying than it should be, by having to click a link that forces reloading of the store page (and you may have to do this several times for several products as their system of storing cookies isn't all that great either).
Then with pre-orders there have been cases where they insist on charging you the full amount TWICE - once when you pre-order, and once when the game is released. They say this is to ensure the funds are available, but if that's the case, there is no need to charge more than 1 dollar for the first transaction. There have also been cases where international customers have had to wait several days following the release of a pre-ordered game until they get it unlocked (while US based customers get it unlocked first). If this is due to regional release date differences, Impulse have never listed as such.
Further, there's some insane regional pricing mark ups on games for which none of the other Digital Distributors mark up in a similar fashion. The most notable are games published by Calypso. They are significantly more expensive on Impulse for international customers than from any of the other digital distributors. Impulse claim this is due to the publisher, but then fail to explain why they are the ONLY service to mark those games up in that fashion.
This is even more suspicious when they claim to be the second largest digital distributor (in terms of market share - they claim 10%), and yet the services they claim to be smaller than them, GamersGate and Direct2Drive do not have this same problem with that publisher. Surely smaller distributors would not be capable of negotiating better publishing deals than Impulse? Right? Yeah, that's what I thought.
In terms of service, regional availability of products, pricing and so forth, Impulse is always my last choice. I'll take GamersGate first, GOG, Steam and then Direct2Drive (sadly, Direct2Drive also suffer a large number of regional restrictions that make it difficult to purchase from them).
As for sales, I see no honest way that Impulse can claim to have started such "weekend" sales. As already mentioned, Steam (and even D2D) were offering frequent sales long before Impulse and even when I first started seriously monitoring Impulse around a year ago, they had infrequent weekend deals (it's only been in the last 8 months or so that they have become a weekly affair). And even then, the titles that Impulse consistently put on sale (and which are available worldwide) have either already had far better sales elsewhere or are of low quality.
If they seriously want "second" place in terms of market share, then need to wake up and realise that there is far more to digital distribution than just North America. Really, it's nigh on impossible for the rest of the world to take Impulse seriously.