There is also the question of turnaround time.
If you special order a new one it will probably take a while (>month) to get it.
Used ones or "floor" models at the dealerships do exist, and are probably "cash and carry".
What are the trade-offs between models (2008, 2009, 2010, regular or Sport) & delivery times?
As far as I know, there was no official Model Year 2009. Basically all of the new 2008s are sold so it would be used only for one of them. The 2010 has a bunch of changes, but the most noticeable would be the switch of the shift lever to P-R-N-D buttons, the move of the VDS from your left knee to the center (under the radio), and the change of the dashboard to show energy-used + speed, not RPM + speed (which was practically redundant in a car with only one gear).
I think the PEM was extensively redesigned between 2008 and 2010 models. I think the A/C was also redone. I heard that motor cooling was also improved. I don't think the new PEM uses motor windings as an inductor anymore for charging, so perhaps no more "reductive charging" royalty to ACP.
Is the Sport worth the extra cost?
That depends on how much you value performance and having the "best of the best". You get 0-60 in 3.7s instead of 3.9s if that is important to you. You also get 1/4 mile in about 12.6s instead of 12.9s. You also get stickier tires and some suspension upgrades for better handling.
What are the current delivery times like?
Why not talk to a salesperson at one of the stores and find out? I don't think there is much of a waitlist anymore, so it is probably as fast as they can build it and ship everything to your nearest dealer. Keep in mind that major parts would come from various places in Europe and have to be shipped to Menlo Park for drivetrain install, and then delivered to your nearest store (e.g.: LA)
Or, should I try to get one used, like from Ebay?
If you are in a hurry and want to save a little money, and don't need personalized options, and don't mind that someone else put some miles on it already.
(Probably not eligable for the same tax deductions either)
I am in Los Angeles area, I would prefer a California car (no rust).
With an aluminum chassis and carbon fiber body, I wouldn't be too concerned about rust with the Roadster.
Also, the LA area is probably one of the largest Roadster markets, so you should be able to find some available.
If you are serious about buying one soon you should go to the LA store and talk to them.
Tesla Motors - Store Locations - Schedule a Roadster Test Drive in West Los Angeles
11163 Santa Monica Blvd.
West Los Angeles, CA 90025
310-473-8337