Saint, please add this info to the main BYOAC page. This is about the third time I've answered it, (OTOH, I tend to think it through more each time, so the info gets better).
First off, if you are using any of the mechanical (click) joysticks, you will want mc-escher's source files and a custom compile. Rotary patch files are available at
http://www.cryptnet1.net/mame/ and MAME R59 source files are available from
http://www.mame.dk/emulators/. (Delete the two -werror flags from the make file to get it to compile).
What Urebelscum said is all right on, but the opto-rotaries are generally a better overall solution. You have 4 (realistically 3) choices of sticks/interfaces. There isn't a right/wrong solution. Your decision should be based on a) how much do you want to spend. b) what interface method can you support, and c) will this be a stand-alone (rotary only) solution or do you want to play other games on it as well.
Here is what I would recommend overall, and then I will provide details/justifications later:
1) prototype stick - best all around.
2) Happ opto-rotaries - generally a more rounded solution, best solution if the rotary joysticks will be your main sticks and money is a factor.
3) Happ mechanical rotaries and Druin's interface - best solution if price is no object, true arcade feel is important, and you want these to be your main sticks.
4) SNK LS-30's and Druin's interface - best solution if you can use a separate panel for rotary games only.
Now the details on each option:
Prototype stick - Not available. This is an option that another BYOAC'er and I are working on. It is a modified Happ stick with two additional microswitches, a click-feel and no additional interface, except for the two additional encoder inputs. Unfortunately the guy that's building them will not have time to make them commercially available. I don't have time/fabrication tools to make them commercially available, and they haven't even been built yet. If we get them working, we might look at finding a way to make them available. Approximate cost was estimated at $50.00- $60.00 per stick.
Happ opto rotaries - Sticks ($40.00 each), Opti-Pac ($40.00) or Gutted USB Mouse ($5.00). The main advantage of this stick is that it is based on the Happ Super so it plays fine for non-rotary games. Also, since the opti-pac will probably be required for a trackball or spinner (and can simultaneously support two trackballs and four spinners with auto-switching), the ADDITIONAL interface cost is FREE. The disadvantage is that it lacks the click-click feel of the true rotaries.
Happ mechanical rotaries - Sticks ($40.00 each) Druin's interface ($68.00). This is also based on the Happ super, so it also plays well for non-rotary games. Note that Druin's interface requires an external +5V source. The main drawback here is price. It's hard to justify $150.00 just to play a dozen or so games in MAME.
SNK LS-30's - Sticks ($15.00 each) Druin's interface ($68.00). Again, note that Druin's interface requires an external +5V source. The problem with this solution is that these sticks do not perform well in non-rotary games. The plus side is this is the cheapest arcade perfect solution. If you can afford a separate control panel just for your rotary joystick games, then go with this method.
Hope this helps!!!