Behringer U-Phoria UMC204HD

While the hardware is well-built and, on paper, offers impressive specs (especially for the price), Behringer provides low-quality software and no ASIO driver. This translates into a rather poor interface (at least on Windows machines - I haven't checked on other platforms) and the need to rely on generic drivers for ASIO, whose quality isn't great.
So, while the hardware has potential, ultimately one gets a mediocre item. It's a pity Bheringeer don't dedicate more effort to the software they supply as that could have dramatically improved the product.

I moved to this from a Native Instruments Audio Kontrol 1 with Mackie HR824mkII monitors. The interface is quite well built and sturdy but Ive found that no matter what I do, the overall volume output is extremely low and I can never drive my monitors to loud level.

Overall the sound quality is pretty good, but the volume problem means Im very disappointed with this interface.

I use this in live settings where it has not been ideal in terms of signal to noise ratio and latency. With a DI between this box and the main PA it's either been a big hum on the channels or a fair amount of noise. On the other hand, it's very compact and does it's job quite alright. The onboard features and easy interface (layout) are nice.

I was not happy with the audio quality and have since installed a Cambridge Audio dacmagic100 which has a vastly better sound.
I still use the UMC 204HD as an interface for midi keyboard recordings and am happy with it for this purpose.