Apple executives on Monday bragged about how how the new iPad has been flying off the shelves over the past few days. If you’re one of those still pondering whether to get one, here’s everything you need to know.

The big question for many techies who may already have the original iPad, the iPad 2, or an Android, is whether to upgrade. Hayley Tsukayama rounds up the advice of some of the nation’s top reviewers:

For anyone looking to buy an Apple tablet who doesn’t already own one, The Post’s Joshua Topolsky said, this is a no-brainer.

“[If] you’re in the market for your first tablet, or upgrading from the original iPad or an Android device, do not hesitate. The new iPad is the most functional, easy-to-use and beautiful tablet that any company has ever produced,” he said. Upgrading from the iPad 2? If you are okay with your screen, network speed and cameras, there’s no reason to rush out right now, he said.

But, says TechCrunch’s MG Siegler, “if you choose not to upgrade (or to spend $399 for the 16 GB iPad 2 now), again, treat the new iPad as if it were Medusa when you’re in an Apple Store. Do. Not. Look. At. It.”

Some reviewers have taken apart the iPad to take a closer look at the gadget’s insides :

Luke Soules, the co-founder of the repair manual Web site iFixit, flew all the way to Australia to be one of the world’s first people to buy the new iPad. The site iFixit is known for its penchant for pulling apart devices, meaning that Soules promptly started to tear into the tablet in order to post pictures of a live teardown on his site.

According to a report from the Herald Sun, the midnight turnout was “modest.” Soules told the newspaper that he was surprised that the lines were longer for the iPad launch.

“I waited 12 hours for the iPhone 4S and I was only 17th in the queue,” he said.

The teardown on iFixit revealed that the new iPad seems to have Samsung screen and found that the new battery has seen a significant upgrade.

“While the iPad 2 housed a formidable 25 watt-hour Li-ion battery, the iPad 3 has upped the ante to the tune of 42.5 watt-hours,” the blog said, speculating that the extra power will go to powering the iPad’s extra RAM and improved graphics processor.

Even though the new iPad has only been out for a few days there are already a number of complaints about features or lack thereof:

No Siri: Many people were expecting Siri on the iPad, so while the voice dictation feature that has been added to the tablet is quite good, users are lamenting that they can’t tell their iPad to schedule appointments, conduct Web searches and note reminders for them.

Storage: The HD display on the new tablet is great, but has also required a boost in the sizes of some apps. Just note before buying that you may not be able to carry quite as many apps as you have in the past.

International users: International users have been complaining that they can’t use their iPads on “4G” networks. The Australian reported that some carriers in Australia, for example, have done away with advertising the 4G features of the iPad altogether, since the airwaves approved for 4G in the U.S. and other countries aren’t the same.

A research firm has speculated that thanks to the new screen and battery, the new iPad is more expensive to make than its predecessor:

Apple appears to be making less of a profit from each new iPad than it did when it launched the previous model a year ago, according to a research firm’s analysis.

IHS iSuppli took apart a new iPad on Friday, the day the device went on sale in the U.S. and nine other countries, and found that the components are more expensive than those of the iPad 2.

The third iPad comes in several versions starting at $499, the same price as the iPad 2 at launch.

Apple has priced all three generations of the tablet aggressively, making it hard for competitors to match its features at the same price. It makes less from each iPad than from each iPhone.

As a whole, Apple is wildly profitable, earning $33 billion in net income on $81 billion in revenue in the last calendar year.

ISuppli said a new iPad with 32 gigabytes of RAM and a cellular modem, which costs $729 in stores, costs $364.35 to manufacture. That’s 9 percent more than the $335 it cost to make the corresponding iPad 2 a year ago, when it came out.

The corresponding version of the first iPad cost about $276 to make in 2010, according to iSuppli’s estimate.

The higher-resolution display and the larger battery needed to support it are the main reasons the new iPad is more expensive than the iPad 2. It has four times as many pixels as the iPad 2’s screen. ISuppli estimates the display costs Apple $87, plus $40 for the touch-sensitive layer.

The new iPad battery has 70 percent more capacity, but the new display consumes all that additional power, so the battery life is the same as for the old model.

If you decide to purchase one, here are some tips about apps that you can download o show off the cool retina display technology to your friends and family, according to Venture Beat:

Apple has wisely collected some choice apps optimized for the new iPad in iTunes, but there are still some glaring omissions from that list. We’ve collected some of our favorite apps, as well as the ones that we think will look best when upgraded to the new iPad’s 2048 by 1536 pixel resolution.

Epic’s sequel to its smash-hit Infinity Blade has been one of the best-looking apps on the iPad since it was first released. Now with its update for the new iPad, Epic’s graphical prowess has even more of a chance to shine. Infinity Blade II shows how the new iPad can seriously be considered a competitor to existing consoles. — $6.99

Amateur astronomy junkies rejoice, the best space app on the iPad is now even better. Solar Walk contains a ton of information about our solar system, as well as detailed 3D models that really take advantage of the iPad’s Retina Display. — $2.99

For the full list, click here.