On Friday October 14, after more than 10 years using BlackBerry mobile phones, I switched to an iPhone 4S running on AT&T's network. Although Siri hasn't exactly lived up to my (probably too high) expectations, and the phone and its upgraded OS are missing some important capabilities, I am unlikely to look back.

What's more, I also have a Samsung Galaxy SII Android phone running on T-Mobile's "4G" (really HSPA+) network. I have a good bit of Android experience, having tested several other phones from HTC, LG, and others, and I have plenty of iOS experience on the iPad. In other words, I'm not a novice; on the other hand, I did have to ask someone on a flight with me what the "lock" button on the iPhone was for (alert sounds, not screen lock, as it turns out).

After a weekend of work and play, the iPhone has become more of a companion than my BlackBerry ever was, and I can't quite put my finger on why. Our company just began allowing the use of iPhones, and perhaps it's this mix of the personal and professional that makes it so compelling. The BlackBerry--for me at least--only hit the personal for the necessities: personal e-mail and calendar integration. Our company, for security reasons, doesn't allow Android devices, but if it did I could imagine the Samsung Galaxy SII also becoming more of a constant companion, even with its quirky user experience.

Based on years of conversations with CIOs and IT managers around the world, my sensitivities around mobile device management and mobile security are particularly heightened. It makes me queasy to give into my instincts as a consumer and end user, rather than as someone who understands the need to protect corporate assets and to protect end users from security and regulatory compliance accidents.

[ Learn more about the iPhone. View iPhone Through The Years: Visual Tour ]

On the other hand, having seen the host of mobile device management solutions, I worry less. That RIM enables hundreds of policies is a comfort, but the hard truth is that most companies deploy only a fraction of those policies, most, if not all, of which are now available in multi-platform device management services, like those of MobileIron, Airwatch, and Fiberlink, just to name a few.

With the caveat that I haven't thoroughly tested iOS 5 (CNET's early iOS 5 review provides a more comprehensive series of observations; I also liked Technologizer's Ideas for iOS 6), and that this isn't meant as a product review or comparison, here are 7 early iPhone 4S observations from a confessed BlackBerry addict.

1.) Getting Started: Simple.

Like my colleague Eric Zeman, Friday work prevented me from jumping into the morass of people trying to activate new phones, and that was probably a blessing in disguise. It took about a minute for my phone to get activated. (See iPhone 4S: My First Night.)

Because my company has to specifically enable new devices on its Exchange Server, Friday night's iPhone 4S activation, while flawless, was incomplete--I wasn't getting corporate e-mail until Saturday. I didn't know how much of my contact database would come over to the iPhone, so I tried using Google Sync--the BlackBerry app pulls in contact information, and then I was able to pull it in on the iPhone. However, this seemed to only pull in some of my contacts, and absolutely no phone numbers. Thankfully when IT activated e-mail, everything came with it.

2.) Siri: Friends With Benefits

I had high expectations for Siri. I still do, but for now I'm less sanguine. Apparently Siri can feed requests to the Web, interact with messaging systems on the phone, and connect to Yelp and Wolfram Alpha. I suppose it's a start, but it does impose some early limitations. On the other hand, Apple has specifically said the service is in beta testing; in short, we should give it some time.

Still, a few early observations. First, Siri doesn't seem as interested in getting personal--for example, she doesn't want to know my name. Maybe that seems silly, but like when Starbucks calls out your name to give you a drink, it just feels better, more personal.

Second, Siri's hooks into messaging don't seem deep. I tried to get Siri to reply to a message in my inbox from someone named "Tim," but because she couldn't find that particular Tim in my contacts, it simply wouldn't work.

Third, while some have said that Siri can ferret out "meaning," that capability is still somewhat limited. For example, I asked Siri to find movie reviews of "Ides of March." She showed me movie listings in my area. I asked for New York Times movie reviews, and she showed me movie listings in New York. Eventually I got her to simply enter my phrase into a Google Search.

Still, simple replies to text messages, Google searches, restaurant searches, and changes to my calendar all worked really well, and that, in itself, is pretty exciting.

Unfortunately using Siri in public still feels a bit like showing off (look at me, I have the new iPhone!). And more intrusive on those nearby than making a phone call.