I have - it's basically a combination of a sewing machine pedal, a variable switch, a pressure regulator valve and an HPLC column and attaches to a nitrogen cylinder. You control the length of the gas pulse with the variable switch and the pressure with a pressure regulator on the cylinder - so it works just as well as a digital injector, except that it is maybe a bit less precise (mostly because there are no real units on the vairable switch, you have to measure the pulses and mark them yourself). There is a bit of trial and error involved in getting the volume you are after out of it (depends also on the thickness of your capillary, but then again, this goes for digital versions as well), but it is super fast, cheap, and can be moved around a lot. So if it is precision you are after, it is not that good, but if you are making your own capillaries and need to adjust parameters a lot to get the desired volume, it's fine.

The minimal volumes you get depend a lot on the diameter of the injecting capillary, but I used pretty thick ones (20-50 um inner diameter) and was able to inject about 5 nl at a time.

If you already have some of the said components, you can also just order the ones you need. Some of the people here didn't quite get why I bought one, since they could put one just as good together themselves. But I think it's good to have something more standard.