This is a very versatile device! You can set it up with your brake on the high friction side for extra friction as well as clipping the carabiner closer to the tubes. You can even set it up to work like a figure 8. Many different combinations to suite your use and rope diameter.
My problem with this device, like any other device with a hard attachment point, is that you have to take the device off the carabiner to hook up or remove yourself from a double rope rappel, or if you are using twins or doubles to belay. This increases the chances of dropping the device and makes it more cumbersome to use, especially on full and multi-pitch climbs. For that reason I will stick with plastic coated cable attachments from now on.

This thing gives a crap-ton of friction. The solid stem keeps it from binding against the carabiner, so it Never jams. Some people have complained on here about how it binds against the carabiner in a wierd way, but all you have to do to fix that is get a mod D-shaped 'biner and clip the stem first and then the rope so that the stem is right against the spine of the 'biner. It keeps the SBGII upright (instead of torqued against the 'biner) the whole time. Gives a $#!tload of friction when rapped as an 8 on a single rope.

I've had this device for over a year now and I'm super happy with its features and its ruggedness. I've used it on fuzzy gym ropes and new, skinny and slippery ropes. It really outshines a regular ATC on new and slippery ropes because it has options for more friction.

Because of the rigid stem, I locks down well, pays out slack really well and doesn't travel up and down the rope and get kinked like a regular ATC.

Very useful for repelling as you have many options for the amount of friction you want.

I use it with an Omega Jake and it does have a tendency to wander over into the crook of the bend, near the spine. You'd really have to not be paying attention for it to completely cross-load though.

It hasn't wore any sharp edges. It also makes a lot of noise on your harness (bonus?) and people always want to try it.

The SBG has four friction settings, depending on whether you use the lower or upper clip hole, and the V-groove or curved side as your brake side. This makes it a very versatile device. On thinner ropes, use the upper hole and V-groove for maximum friction. On thick 11mm gym ropes, I found using the lower hole and the V-groove was the best combination. Taking out slack is much smoother than an ATC - the SBG never binds up, even after a climber gets back on the wall after locking off to catch a fall. I also find the V grooves give better holding power than the ATC. Holding onto a hangdogging partner is pretty much effortless, where I would have my fingers aching after a while doing the same with an ATC. Lowering with the SBG was also much smoother and less jerky, with climbers starting at a hundred pounds and going up to twice that.

One thing to note is that the SBG might be more prone to binding up or crossloading the biner due to its solid stem. For that reason, I HIGHLY recommend combining it with a DMM Belay Master carabiner, which has a plastic shield to prevent crossloading.

I bought it because it is forged from a single piece of aluminium, and not a length of wire secured (hopefully well) to another piece of non similar metal. (ever see what happens to a steel when it is kept in contact with aluminium for a long period of time?) The device allows you to rapidly pay out rope to your climber without too much effort, and minimises the chance of rope/ATC/biner jam-ups because it does not move up and down in relationship to your biner. The solid design keeps that distance constant. It has two fricition slots of different size on each side that will cover most (but not all) rope sizes and climbing/rap needs. Setting up to rap down does require somewhat more work and planning than with some other designs of ATC's, but every design is something of a compromise. Work out your rap setup before you're at the top of your first climb with the SBG. That said, it is at it's best in the gym and for shorter outdoor climbs. When you need to, your partner can hang for a long time before you'll get too tired. Price and versatility add up to a good value.