It's going to be a busy week for tech enthusiasts: Over a 24-hour span on Tuesday, Microsoft will begin selling its second-generation Surface tablets and accessories, Nokia will announce several new devices (including its first "phablet" handset and tablet), and Apple is expected to announce new versions of its popular iPad and iPad mini tablets.

I've had loaner Surface 2 and Surface Pro 2 devices (as well as a few new accessories) in for testing since last week, and you can read about my initial impressions on the SuperSite for Windows. But here's a quick rundown.

Surface 2 presents perhaps the biggest changes compared with the original device, although none of the changes I see here are particularly revolutionary. It is thinner and lighter than the Surface RT it replaces, and it offers even better battery life. But the biggest improvement is the screen: It's now a full HD, 1080p display with vivid color reproduction. Check out "Microsoft Surface 2: First Impressions and Photos" for more information.

Surface Pro 2 is the more evolutionary update. It is physically identical to its predecessor, and just as heavy, and although the screen offers the same 1080p resolution as its predecessor, it too offers richer color reproduction. The biggest improvement for the Surface Pro 2 is the battery life: Where the original Surface Pro could deliver about 4.5 hours of life in real-world use, the Surface Pro 2 delivers between 7 and 8 hours. (I'm still testing that aspect of the device.) You can find out more in "Microsoft Surface Pro 2: First Impressions and Photos."

Microsoft will also begin selling a new collection of Surface accessories starting Tuesday. The new Type Cover 2 and Touch Cover 2 are both slimmer and lighter than their predecessors, but both now feature a nice backlighting feature, too, and the former uses a new felt-like coating on the wrist rest that I prefer. I'm also testing the Arc Touch Mouse Surface Edition, and spent a bit of time with the Power Cover and Docking Station last week. You can read all about it in "Microsoft Surface 2 Accessories: First Impressions and Photos."

Also on Tuesday, Nokia will hold a special event called Nokia World in Abu Dhabi at which it is expected to launch several devices. Key among these are the Lumia 1520, a 6" Windows Phone 8-based phablet with a 1080p screen, 2GB of RAM, and a quad-core ARM processor. Leaked shots of this device suggest an interesting cross, design-wise, between the Lumia 920 and 925, and the device will feature a 20-megapixel camera that could rival that in the Lumia 1020.

Nokia is also expected to announce its first tablet, the Lumia 2520. First revealed on the SuperSite for Windows, this tablet will run Windows RT 8.1 and will feature a quad-core ARM processor, 2GB of RAM, a 10.1" 1080p screen, and LTE broadband options. And like the Surface 2, it will be offered with a battery-powered keyboard cover.

Nokia is also expected to announce a number of other handsets, the most notable of which is the Lumia 929. This device, aimed at the US wireless carrier Verizon, will also offer 1080p capabilities, but in a 5" display, and a 20-megapixel camera. A follow-up to the popular Lumia 520, called the Lumia 525, could also debut at the show.

Meanwhile, Apple is crashing the Microsoft party with its own special event on Tuesday at which the company is widely expected to unveil a new high-resolution "Retina"-based iPad mini and a thinner fifth-generation full-sized iPad. But Apple will likely unleash the rest of its pending product updates at the show, too, including a new version of Mac OS X called Mavericks, new Intel "Haswell"-based Macbook Pro laptops, and possibly a refreshed Apple TV (or at least new entertainment initiatives related to Apple TV).

Of course, the iPads are the big news here. Apple jumpstarted the current tablet market with the release of its original iPad in 2010 and has seen sales explode since, but the market has quickly commoditized around much-lower-cost devices running Android. Apple's share of the tablet market fell to 32 percent by mid-year. It will continue falling, too, as tablets push forward to replace PCs as the mainstream computing device of choice and the competition gets fiercer. In addition to the Microsoft and Nokia devices mentioned above, Amazon, Google, Samsung, and many others have or soon will launch their latest tablet initiatives, all aimed at grabbing a piece of the market from Apple. Tablet sales could overtake those of PCs within two years, industry analysts believe.