Retro Instruments 176 Tube Limiter is a single channel compressor/limiter. It is an all analog piece of gear that offers up a ton of features and parameters to mold your tone with. I can't say anything about what types of connections it has because the one that I have used was pre-racked in the recording studio that I used it in and I didn't have anything to do with racking it up. In a traditional rack space, it will take up two spaces.
Using the Retro Instruments 176 Tube Limiter wasn't too hard for me but I have a lot of experience with compressor/limiters. That being said, I don't think that most users will have trouble figuring out how to use this piece of gear. The 176 has knobs for input, output, compression ratio, attack, release, and metering. The unit also has a number of switches including for choosing the mode. I haven't seen a manual for the unit so I can't say how well put together it is, but unless you are a beginner with compression, I don't think that you need it.
The sound of the Retro Instruments 176 Tube Limiter is just about as good as it gets for compressor/limiter. It has an extremely clean sound that can be applied to just about any situation where you would want to add some compression. I've had great success using the compressor on drums, vocals, and guitars, and judging by the top notch tone I would say that it can be used for just about any application. There are enough parameters to play with that it makes it a versatile piece of gear where the sound can be manipulated in all sorts of different ways...
All in all, I've got no complaints about the Retro Instruments 176 Tube Limiter. I'm not sure if it is modeled after the 1176, but judging by the name and the overall make up of the unit, I think that there is definitely some influence there. I'm not familiar with too many other products that Retro Instruments has to offer, but the 176 is truly a special piece of gear. While the price is not cheap, I would definitely recommend this to anyone looking for a top tier compressor.