Sorry for the late reply, haven't checked the thread for a few days now.
1) Give us the option to use C or F.
[snip]
1) Celsius and Fahrenheit. Normally I'm all about metric, but as a user of smcFanControl, I switched my display to F for the past 2 weeks and only recently got used to it. I wanted to compare the side-by-side temp readings but had to change my smcFanControl settings to do that. This made me think that for people that are more standard-minded, a unit toggle couldn't hurt. I don't think anyone routinely uses Kelvin, but you could throw that there as an option too. (iStatPro has a Kelvin setting- it seems enough people use iStatPro that Kelvin could conceivably be used by more than a handful of users.)
That's something I wanted to implement, but no one was requesting it.

Now that you mention it, I'll let the user choose the preferred unit.
In the set target temperature dialog, I think it would be better if we had some more options:
2a) Instead of a strict target temperature, we should be allowed to set minimums and maximums.
2b) Instead of only setting the target for the CPU, we should set targets for the GPU and enclosure.
[snip]
2) There seem to be two general reasons why people would like an applet like smcFanControl (the established free temperature control) or UltraFan. Some people think that Apple's preset thresholds are too high and would rather keep their components (and laps) a little cooler in the name of longevity (and comfort). Other people don't like how their fans spin up all of a sudden. They get used the their fan at a fixed speed and the noise fades into the background. So under some workloads, their fans speeds fluctuate and get more annoying. With smcFanControl, I just set my fans to go at 4800rpm minimum and let my temperatures wander. The noise fades into the background and for the most part, I don't get surprised by a sudden increase in fan speed.
If you had temperature ranges available, you address the noise issue. Ie: target 60C, min 58C, max 70C. UltraFan could make *very* gradual changes to fan speed within the 58-70C range so that we don't hear sudden changes in fan speed. As I type this long-winded reply, I've noticed my fan spin up and down a few times and have become irritated by this aspect of UltraFan. I've read (in other forums) that some people use their MBPs in a recording studio type setting. I'll admit that I don't know too much about audio recording, but I would think that it's easier to "clean up" fan noise from a recording if the fan noise is relatively constant.
Secondly, if you allow us to set target temperatures for the CPU, GPU, and enclosure, we would be able to tailor UltraFan to our preferences. When I'm lounging around with my MBP on my lap, I don't care where my CPU or GPU temps are. I care most about how hot my lap is. iStatPro shows 3 different sensors on my MBP for the enclosure, so you'd have to figure out which sensors are associated with the location of the CPU and GPU. (I'd be welcome to beta test this). Anyway, the point is, sometimes the enclosure temperature matters to a user far more than the CPU/GPU temperatures. This would add a fair amount of complexity to your settings panel though. Now you would need to also allow us to prioritize which temperature trumps which. (Ie: You could hit a CPU minimum of 70C before you hit an enclosure maximum of 45C. So your crotch would be on fire but your CPU is happy as a clam. End result: mad user.)
The range of temperature sounds like a nice idea.
That would allow for more gradual changes, as you state, within that range. When exiting the maximum threshold set, however, UltraFan would need to make bigger jumps, but that too sounds ok. As a downside, this would probably create some confusion, but I can design an appropriate interface for it.
As for 2b), I have to find out how to retrieve precise data from different sensors, if found. Haven't looked much into that, but I will.
3) You could have a slider-style control (by slider I mean the kind of element you have for choosing the target temperature) to let us choose whether we want more continuous or less continuous adjustment of fan speeds.
4) Simplify your menubar display. Or give us some different templates.
3) Option for gradual vs rapid fan speed change. This partly is related to the "my fans keep spinning up and down and it's more annoying than if they were just on all the time" crowd. This kind of setting would tell UltraFan whether to change fan RPMs in increments of 500rpm or something closer to 100rpm, and whether these adjustments will happen every 1 second or 20 seconds. (Ie: Min CPU 58C, target 60C, max 70C. 100rpm increments every 20 seconds might be enough to keep me between 58-70C most of the time without me noticing my fan speeds changing.)
4) Tweak the menubar display. I don't personally care for 2-decimal point precision in temperatures. But I do like knowing how fast my fans are running. Someone else might not care how fast their fans are running. So you can either give us a bunch of options or take them all away. Download smcFanControl and have a look at their various layouts. Something like that would be a start. But you could improve on it.
There's a problem with 3). If I let the user choose how aggressive UltraFan should behave, then it's more likely for it to pass the threshold, thus creating a conflicting behaviour with the logic you expressed in 2a).
That could be applied when in the selected range, but I don't think that would make much sense there, as UltraFan would already go on the gradual route.
I like the 4) also, but don't really think the user has to be notified about the rpm of the fans.
For the record, I use smcFanControl's multiline display with temperature and fan speed. Here's how I'd make it better. Line 1: Current temp rounded to nearest degree. Black font if at target. Blue font if under target. Red font if over target. Various shades of Blue-Black-Red to correspond with how far away from target. Line 2: Fan speed of fastest fan, in black font. Similar color changes to tell us whether the fan will be going faster, slower, or the same. Or, to be kind of awesome, italicize it if it's going to go faster and left tilt italicize for slower.
I'm going to implement a similar system with the beta version of 8.3. When ready I'll send it to you via pm, if that'so ok.

Thanks for the feedback and the suggestions. Appreciated. Feel free to express your opinion on my reply.
I've been using Ultra Fan for a month now. The issues described on page 3 of this thread were, I discovered, unrelated to UltraFan. I like it much better than SMC Fancontrol and intend to continue using it.
However, I do think that a gradual fan acceleration as mentioned by the previous poster would be of benefit. It seems to me that UltraFan increases fan speed a little vigorously at times.
At other times, FanSpeeds seem to increase without justification (judging by the ambient temperatures as reported by iStat Menus)
I appreciate that a change like the one described may be difficult for the developer to implement but perhaps Lost Soul might consider it for the future.
Thanking you, LS, for a great app.
I can implement a more gradual and intelligent system, and seen that may of you would like it, I'll code it. Again, thanks for the feedback and appreciation.
