Between Tesla Motors' (NASDAQ:TSLA) practice of releasing a lengthy letter to shareholders every quarter and management's habit of spending over an hour fielding questions from analysts during quarterly conference calls, the electric-car maker's quarterly reports are usually packed with plenty of commentary for investors to mull over. Tesla's first-quarter report earlier this month was no exception; Tesla CEO Elon Musk and other Tesla executives discussed key topics, including the Model X launch, the Gigafactory schedule, growing demand for the Model S, spending plans, and even an update on the Model 3.

Here are some of the most notable quotes from Tesla's first-quarter earnings report.

Model X
Musk said during the company's first-quarter earnings call that he expects Model X customers to finally be able to configure the specs for their order in July. Furthermore, he said first deliveries of the fully electric sport utility vehicle should begin in September.

Model X prototype. Image source: Tesla Motors.

Reflecting his bullish comments about Model X in the past, Musk is still euphoric about the SUV.

"But I really think the X is really going to be a great car," Musk said. "And I just drove the latest prototype today and it's like, wow. This is by far the best SUV."

Importantly, Musk says Tesla is "paying close attention" to some of the SUV's unique features in order to make sure they're not an issue when Tesla ramps up production, "particularly the falcon wing doors and the second-row seats."

Gigafactory construction progress, May, 2015. Source: Tesla Motors.

The schedule for Tesla's currently under-construction Gigafactory, which is purposed to produce more lithium-ion battery capacity under one roof than was produced in the entire world in 2013, continues to improve. Initially, the first cells were supposed to begin production in 2017. But in the company's third-quarter letter to shareholders, Tesla announced it has moved the beginning of cell production to late 2016.

And now Tesla is even further ahead of schedule.

"[S]teady construction progress continues at the Gigafactory, and together with Panasonic, we now expect to start complete battery manufacturing, from cells to modules to battery packs, in 2016," reads Tesla's first-quarter letter to shareholders.

Model S
Demand for the Model S continues to rise, Tesla emphasized in the first-quarter letter:

We continue to see growing Model S demand. In Q1, both North American and European orders were much higher than Q1 last year, despite limited availability of 85D and before the announcement of 70D. ... Recently, order rates have accelerated even further with greater availability of 85D and the launch of 70D. This is especially encouraging as potential customers in many markets have yet to experience these products first hand. 70D has only been shown in North America, and our all-wheel drive cars will not be available in right hand drive markets until Q3.

Demand for Model S was robust enough in Q1 for the company to maintain its optimistic outlook for vehicle sales growth in 2015, expecting to deliver 55,000 Model S and Model X vehicles combined, up 74% from 2014 vehicle deliveries.

Model S. Source: Tesla Motors.

Tesla said it is sticking to its plan to spend $1.5 billion in capital expenditures this year. The aggressive investment will go toward expanding production capacity, Model X tooling, Gigafactory construction, and a growing footprint for Tesla's stores, service centers, and Supercharger network.

Tesla predicts operating expenses will soar 10% sequentially and 45% to 50% for the full year. Notably, however, the company predicts sales will grow even faster, leading to better operational efficiency.

"Our operating leverage is expected to improve this year, with revenue and gross profit both growing more quickly than operating expenses," reads the Q1 letter.

Model 3
Anyone following Tesla's story closely knows one of Musk's long-term goals at Tesla is to reach a point where the company can economically produce a more affordable fully electric car with over 200 miles of range at volumes in the hundreds of thousands. Tesla has dubbed this vehicle Model 3. As the vehicle is still in the early stages of development, little is known about the company's timeline for Model 3 other than that it plans to bring it to market in 2017.

But in the first-quarter call, Musk shared some new information on Model 3, finally revealing the company's target month for when it plans to show the vehicle to the public for the first time.

"We are hoping to show off the Model 3 in approximately March of next year," Musk said. But he warns, "don't hold me to that month, but that's like -- that's our aspiration.

The launch itself, Musk reiterated, is still scheduled for 2017.

"Late 2017 is probably more realistic," Musk noted.

All five of these items are important aspects of Tesla's business for investors to keep an eye on. In the coming quarters, look for Tesla to continue to provide more color on these key areas.