I've spent the better part of the past two months with a Verizon MiFi close at-hand.  For those of you who don't already know, the MiFi is a portable WiFi hotspot that gets its bandwidth over a mobile data network. This device, about the size of 4 credit cards stacked atop one another, is currently offered by both Verizon and Sprint, though I have only had occasion to test with the former.

The Speed

The first thing I'll say is that the speed isn't really the most important feature of this device for me, then I'll go on to explain why I'm wrong in that assertion. In comparison to your DSL or Cable connection, the MiFi will almost always lose, but it almost always wins against AT&T's 3G network used by the iPhone 3G and 3GS.  In testing here at the TMO Towers East in Durham, New Hampshire, I got the following speeds:

You'll see that downstream is approximately the same for both of these networks, but upstream is almost double on the MiFi and -- even more important -- ping times are about half. In a nutshell, ping is a test of how long it takes to send a piece of data out and get a response back. When dealing with "chatty" protocols like email, web surfing, and Twitter where you're sending a request for a small piece of data and waiting to get that back, an additional quarter-second of delay on each one of those can add up pretty fast.  You'll note that on my office WiFi connection my iPhone gets ping times of 79ms.  That's pretty typical (in fact, it might be a bit slow for normal WiFi) and is a big part of why your Internet experience is so much different on 3G than it is on WiFi at home or work. With the increased upstream and reduced ping times, the MiFi definitely has a much faster "feel" to it than AT&T's 3G.

Battery Life

Verizon claims the MiFi will run off its battery for up to 30 hours in standby mode and 4-5 hours of active data use.  In practice, we got pretty close to these numbers.  After attending a 4-hour concert, the MiFi still had over half it's battery left (we spent a good amount of time actually watching the show, and my wife and I Tweeted a bit between tunes and sets).  The battery can be charged with the included A/C adapter or simply over a powered USB connection (with the included custom cable), so it's pretty easy to find a way to charge it up when it gets low.

The Kicker

Now that we understand how it all works, let's not waste any more time and get to the point.  Why is this the best accessory for the iPhone (and your Mac)? Well, there's no better device for mobile communications than the iPhone ... except when you're in a big group of people and, you know, everyone else has an iPhone, too.  If you've ever experienced this, you'll know that having 5 full bars of 3G service means nothing with regards to your ability to, you know, actually send and receive any data. Get more than a handful of active iPhone users in close proximity and data throughput on AT&T's 3G goes from pretty-good to non-existent. It's situations like trade shows, concerts, train rides, airports and the like where the iPhone's popularity works against it... and that's where the MiFi is invaluable. In the two months since I've been using it, I've attended WWDC (where we used the MiFi to facilitate our keynote coverage), a few concerts, and more than a few train rides all where AT&T's service went to heck yet the little MiFi sat happily in my briefcase or pocket providing WiFi to not just me, but up to 4 other people simultaneously (and securely!).

And since the iPhone's battery lasts longer when using WiFi versus 3G, you get a little extra benefit there, too. Oh, you heard that right: when using the MiFi the iPhone thinks it's on a WiFi network. This means all those apps that are intentionally crippled so as not to work over 3G will happily beam their data across the MiFi.  Just make sure you don't go over your allotted bandwidth or it will cost you!

The Price

Verizon has put together some interesting pricing for the MiFi.  There are "traditional cell-phone" style options where your price lowers depending on the contract length. In return for a 1-year commitment, the MiFi has a net purchase price of $169.99.  With a 2-year commitment you can bring that down to $99.99.  If you want no commitment, the price is $269.99.

There are two monthly plans available for anyone who purchases the MiFi. $39.99 monthly gets you 250MB per month and you'll pay $0.10 per MB in overage costs. $59.99 monthly gets you 5GB (5,120 MB) per month and your overages are only $0.05 per MB.  

Where Verizon's MiFi options depart from the norm, however, is when you don't have a contract.  Purchasing the no-commitment MiFi for $269.99 gives you access to a third payment plan: $15/day (24 hours) with no bandwidth limits. For the occasional traveler, this now becomes a very attractive option.  Instead of paying $6 in the airport or coffee shop to get on a WiFi hotspot and/or $5-$20/day for crummy hotel WiFi, you can now use the MiFi and provide your own bandwidth.  I tested this in a San Francisco hotel room recently, and it worked swimmingly for both my iPhone and my MacBook Pro. 

Expensive, and worth it

Given the MiFi's features and inherent benefits, I find myself having a hard time imagining life without it.  It doesn't come cheap, but it immediately became the most valuable iPhone and laptop accessory gadget in my portable arsenal.  It's small, lightweight, easy-to-use and fills a huge void I regularly encounter when traveling. For me, it falls into the "why haven't they done this sooner?" category, and now I'm just glad they have.