I have used UFG for at least 4 years. Very good stuff, it has a few tricks to it like most non standard dev.
I use it replenished, but the replenisher has been discontinued. I'm fairly certain that its possible to use the stock as a replenisher but haven't worked that out yet, I still have a few cans of the replenisher left.
It does produce a speed bump, yes that is correct, Tri-X I rate at 1000-1600 depending on the lighting.
Even though it makes a speed bump, negs that are over exposed are still very printable, the grain never reaches 'brick wall' status. This is only applicable to optical printing, where you can let the neg get an extreme amount of light, scanning you have to be more careful not to go to far unless you have a strong lamp in the scanner!
The grain size is pretty close to Rodinal, but I'd say that UFG has a bit more 'edge' to the grain. On very fine grain film it gives a pleasant texture and on coarser grain film that extra edge gives it a very nice crispness.
Agitation is a controllable variable that you need to focus on. Initial strong agitation for the first 30-45 sec (fuji films need more IMO) and then progressively softer and lighter agitation is what works well for me. Over agitation especially at the end of the development will take the highlights dense, very nice when looking for a bit more low light detail. Time and temp need to be pretty tight as well, keep in mind that the recommended times are based on 69.8 degrees F and not 68, I make a bit of adjustment (10%) as my replenished batch gets seasoned.
Overall it is a very good developer, very stable and long lasting. I mix up a liter (quart) and replenish that for at least a year, my record is 2 years. I used to hear about this developer being used in newspaper darkrooms in deep tanks and I can see why: Stable, super long lasting, speed boost, fine grain especially for the speed, smooth tonality.
Here is a link to my blog that has a very low light image shot on Ilford HP5+ with a Zeiss Planar ZM 50mm on a Leica M4, film rated at 800, printed on fiber and then the print scanned. Web jpeg doesn't do the print justice, enlarge the image to see the smooth but apparent grain.
http://four-silver-atoms.com/2012/02/24/twirl-st-regis-princeville-hanalei-kauai/
Send me an email from my blog if you want more advice on UFG.
Oh, in case it's in question, I've extensively used Diafine and vastly prefer UFG.
