If you have watched any television lately, you have probably seen an ad touting the "lightning-fast speeds" of 4G networks. What is 4G? That's a matter of some debate, but it has become a catchall term for the next generation of wireless networks being rolled out by the telecoms.

Over the past few months, hardware makers have begun to release smartphones, tablets, and other gadgets designed to make the most of 4G. I got my hands on two of the devices, the Samsung Epic 4G smartphone and the Dell Streak 7 tablet, while attending the Consumer Electronics Show in Las Vegas in January and took them out for a spin.

Samsung's Epic runs on Sprint's 4G network, which is available in about 70 cities nationwide. The Android phone, which has a 4-inch touchscreen, ran at an impressive 5 megabits per second during my tests. Video chats using the included Qik app came in loud and clear, and websites geared for mobile access loaded instantly, even on the lower level of a Las Vegas parking garage. When I switched the phone to 3G mode, it ran at about 1 megabit per second, within the range of most 3G phones, and video calls paused frequently or dropped out. Score one for 4G. Perhaps the coolest feature of the Epic is its ability to become a Wi-Fi hot spot for up to five other devices with the press of a button. I connected my laptop to the hot spot and tested it in some odd places, including a convention center bathroom. In every case, the signal stayed strong.

I had a similar experience with the Dell Streak 7, a new Android tablet that runs on T-Mobile's 4G network, which is available in 100 metropolitan areas. During Qik video chats, speeds reached 7 megabits per second, and videos looked crisp on the tablet's 7-inch touchscreen, though the audio did not work during one call. Like the Epic, the Streak can be used as a Wi-Fi hot spot for up to five other devices.

The Epic costs $200 after a $100 mail-in rebate with a two-year Sprint contract. The Streak 7 costs $200 after a $50 mail-in rebate with a two-year T-Mobile contract or $450 with a contract-free prepaid plan from T-Mobile. Both devices have very short battery lives. The Epic lasted four hours on a full charge during my tests. A fully charged Streak 7 lasts for four hours of video play.

The bottom line: If you live in a city that's wired for 4G, and you're in the market for a souped-up smartphone or tablet, spring for a 4G device. Otherwise, wait until prices come down and the network rollouts are complete. Given that dozens of 4G devices are expected to launch this year alone, you will have plenty of choices.