I've had the ASM G1-x for a year or so and it's been fantastic. Very easy to use. The Sedra pump that comes with it really makes great small bubbles.
I read that for tanks under 200 gallons pinwheel or needle wheel skimmers (like the ASM) are the way to go but that spray inject technology is better for bigger tanks.
If I wasn't upgrading from my 125g to a 215g I would have happily stayed with the ASM G1-X. I think that skimmer was just under $300 new. Torn between selling it or keeping it as a back up.
Not the cheapest, not the most expensive. I think the company has been around for 30 years or so so not a fly by night thing either.