we've installed and run many of these (different brand, same product afaik). they work but: they need replacing regularly, so dont overpay for them. If you ride tremendous amounts, you'll probably want to buy something else next. the machining isn't stellar (the area that contacts the chain). You can ruin them in seconds if you get a chain drop and just power through stupidly (a friend did that, it bent the small chainring, bin).
we've used 50/34, 52/36, 53/39. they're perfectly fit for function if you set things right. depending on the season i run different gearing, so paying under 25 eur per set for me is very compelling.
when you install them, there's a bit of play, so make sure you tighten the bolts in a way to not have play when pedaling forward. And use loctite, as it's the sort of bolt that gets loose and results in creaks.
i use waxed drive trains.
