UPDATED: we've now published our own definitive Palm Pre review

America has gone Palm Pre crazy today, as the much-anticipated iPhone-like handset finally went on sale across the country.

Palm Pre review articles are already popping up on US websites - many of which are slightly less positive than expected.

There's also been some bad news for people wishing to buy the Pre on launch day. Early reports suggest that there are not enough Palm Pre handsets out here to meet demand, with some people leaving Sprint, Walmart and Best Buy stores empty handed.

The wireless Touchstone charger – which enables users to charge the Pre without plugging it in to anything – is said to be an even rarer commodity.

The early sales rush is down to the Pre garnering unprecedented amounts of hype and praise from all-comers, ever since it was announced at CES in January.

Early Palm Pre reviews have been positive - but many people are saying the Pre does not live up to its billing as a genuine iPhone killer.

The Engadget Palm Pre review was an overall positive one: "Just like the iPhone's notches up the ladder, and the G1's contributions, the Pre moves the game forward in a very real way.

"We know this won't be the last of the webOS devices, and we know that as Palm improves its products, so will Apple, RIM, Microsoft, Google, and the rest of the smartphone gang. Unfortunately for them, their work just got a little bit tougher."

And Gizmodo says that the Palm Pre's screen is "the best multitouch screen" they've ever seen, but was slightly more reserved when giving its final verdict:

"The Pre," it says, "may have hardware that's worse than the G1/G2, but the whole package—the software and the hardware—isn't bad. It's good. It's different. That's something we can get behind. I can't wait to see what Palm gets dealt in their next hand."

But Wired US questioned the Pre's battery life, stating that in its review that the Pre typically can only manage a day's usage:

"A morning's worth of heavy use may leave the Pre powerless by afternoon. I've been testing the Pre for less than a week, and typically, the battery meter hits the red zone before sunset," its review says.

And the Wall Street Journal said it thinks the Pre is a brilliant phone – but that it still has some improving to do:

"All in all, I believe the Pre is a smart, sophisticated product that will have particular appeal for those who want a physical keyboard. It is thoughtfully designed, works well and could give the iPhone and BlackBerry strong competition -- but only if it fixes its app store and can attract third-party developers."

The New York Times Palm Pre review meanwhile, was similarly sceptical, saying that while the Pre is a promising handset, it's still no iPhone killer:

"The Pre will be a hit, but the iPhone isn't going away. First of all, Apple's lead of 20 million phones will only grow when the new iPhone 3.0 software (and, presumably, a third iPhone model) come out shortly.

"[It also] has its annoyances. Opening certain programs can be very slow — sometimes eight or nine seconds — and there's no progress bar or hourglass to let you know that it's still working."

And the tech-experts at CNET US give the Pre 3.5 stars out of 5, citing performance niggles as the main reason for a disappointing score:

"Despite some missing features and performance issues that make it less than ideal for on-the-go professionals, the Palm Pre offers gadget lovers and consumers well-integrated features and unparalled multitasking capabilities. The hardware could be better, but more importantly, Palm has developed a solid OS that not only rivals the competition but also sets a new standard in the way smartphones handle tasks and manage information."

And finally, USA Today says that the Pre could pilot Palm to smartphone glory:

"The first Palm Pre will certainly give the iPhone and other rivals a run for their money. To be sure, there are areas where it could improve: Bring on the apps.

"But Palm has delivered a device that will keep it in the game and give it a chance to star in it."

TechRadar will publish its own in-depth review soon.

Read more Palm Pre stories on TechRadar:

Palm Pre goes on sale in the USA

10 touchscreen rivals to the Palm Pre

How the Pre could revive Palm's fortunes

Palm unveils the Pre - a genuine iPhone killer

O2 to launch Palm Pre in the UK before Christmas?

Hands on: Palm Pre preview

Palm Pre can sync with iTunes like an iPod

Palm Pre vs Apple iPhone: the verdict

And more Palm Pre stories...