FYI, I have gone through the process with Alliant and with Lightstream and found the following:
Alliant is very easy to work with, and approved an $80k loan for me which was 84% of the LTV as they only used $95,500 as the vehicle price. That was the base price for the 90D I ordered, I don't know exactly why they used that instead of the full price including all the options I had selected. Perhaps it just didn't matter since I wasn't trying to get 100% financing or anything.
I found Alliant's hard-ish sell on GAP insurance a bit unpleasant. I passed on it rather than signing up and having the option to cancel it up to 60-days after funding. Pretty sure it's useless to me but in any case they were not willing to send me any written terms/conditions for the program (the rep would only discuss the terms over the phone) prior to including it in the funding documents. Not the proper way to handle things in my book, so I passed.
Lightstream approved the same terms but for an unsecured loan at 3.09% for 72 months, also a very easy/quick approval process. I sent them the Alliant pre-approval email I had gotten to consider for the Rate Beat program but they said I needed an official offer letter from the other program before they'd consider the rate beat. This was a bit of a hassle, since Alliant did not provide an official offer letter nor any other documents unless they got a final MVPA from Tesla and went through the final loan approval process with me and sent the actual loan documents to sign. So I took those additional steps, had my DES set up the MVPA with Alliant as the lender (which was my plan, as I thought Lightstream would find Alliant's Tesla-only loan program was specialized and therefore didn't qualify for their Rate Beat.) I sent that along to Alliant, got the final loan documents for the Alliant loan, sent that to Lightstream... and
within under 10 minutes got an approval email from Lightstream amending their loan offer to 1.39% for 72 months for an unsecured loan.
I was pretty surprised by this. But that suits me fine, as 1) it makes selling down the road a smaller hassle with no lien to satisfy, 2) it gives me some more flexibility on insurance policies (I usually do high deductibles but that'd be limited to $1000 by the Alliant terms), and 3) it offers some advantages if god forbid a catastrophe down the road lands me in financial hot water. Oh, and it saves me 0.1% in interest!
Frankly, I think Lightstream/SunTrust is totally nuts to offer anyone - even someone with excellent credit - an unsecured loan at 1.39% for 6 years (or for any term length for that matter.) But, I'm not running nor am I investing in SunTrust, and perhaps the net impact of offering this program is positive for them despite the occasional situation like this one. In any case, that looks like the path I'll be taking when I finally get my hands on my Model X (looking like May 31st delivery date.)