I'll admit that my first reaction to hearing AT&T's announcement was more curiosity than disappointment. I'm a very light data user, so the idea that I might start saving $15 a month appeals to me. After talking to Bloom, I'm even less concerned about potential overage issues than I was early this morning. It looks like AT&T has addressed many of the running-over-your-limits issues that customers have encountered in the past.

Admittedly, heavy data users will be hardest hit. Existing unlimited plans will be grandfathered in but new ones are not an option. If you've relied on AT&T's unlimited plan, you need to maintain your account or act quickly to establish one before the weekend. 2GB data plan users who use the new tethering option will especially have to watch their data volume.

Here's our complete round-up of many of the switchover details that you'll need to know.

Will the new data plans be prepaid or postpaid? Outside of the iPad, these are postpaid plans. The iPad will continue to offer prepaid data plans. Prepaid data is data you buy on a month-to-month basis rather than a contract-based plan where you pay at the end of each month.

What is changing on the iPad? As of Monday, you will no longer be offered the $30 Unlimited data plan on the iPad. Instead, you can opt in for a $25 30-day 2GB plan. However, if you have already signed up for the $30 Unlimited plan and are set with the auto-renew option in place, your unlimited plan will continue to renew for the indefinite future. Unlimited customers will not be cut off. Beware: if you cancel your auto-renewing plan, you will not be able to re-join it after Monday.

What about the iPad $15 250MB 30-Day Plan? The prepaid iPad $15 plan will not be affected at all by these changes. You will continue to receive 250MB (not 200MB) after the changeover for the same $15 cost.

What happens if I use over 2GB in one month on the iPad now? You will be able to purchase another month for another $25, with the data clock starting a new 30 days when you do so.

Will my unused data roll over? It will not, neither on the iPad prepaid plans nor on the iPhone (or other smartphone) postpaid plans.

What happens if I exceed 200MB on my postpaid plan? According to AT&T's Seth Bloom, you will be able to call in or hop online and change that month to the 2GB plan so long as you do so before the end of that billing cycle. So if you have a bad month (or a really good month -- it really depends on how you look at data flexibility), AT&T will offer more overage flexibility. If you do not do this, you will be charged $15 for each 200MB you use -- and that can quickly add up to a lot of ouch. As Bloom added, "You can keep going back and forth between the two tiers." So if you opt into the 2GB plan for a month, you can opt right back out the next month without penalty.

Can you do the reverse? Can you hop out of the 2GB plan to the 200 MB one when you see that you haven't used much data that month? Bloom is checking into this for us, so right now our answer is: "We don't know." Sorry.

Can you add tethering for just a month? Say when we travel? Tethering does not require a contract, so you should be able to add the feature and remove it as needed for as many months as required.

What if I exceed 2GB on my postpaid plan? AT&T sells 1GB "bucket" increments at $10 each. They will charge towards the current month and will not roll over at the end of the month. So watch your billing cycle end-date.

Why 2GB? Why not 5GB or Unlimited? Bloom explains that this was a change in coordination with the other plans AT&T rolled out, and was not specific to iPad or iPhone users. "We looked at the amount of data that people are using," Bloom explained, "And balanced what users were using in terms of [cell data] versus wireless. We think it's a very very good plan even with 2GB." AT&T set the 2GB limit to match what most users were commonly using. The plan allows most users to save a few bucks a month, with only the most data-demanding users paying a premium on top of what was previously offered.

What happens to users on the current iPhone unlimited plan? They get to keep that plan for the forseeable future. The changes do not affect iPhone users who are currently signed up for the $30/month plan or 2G iPhone users on the $20/month plan. If your plan lapses, however, so will your ability to keep unlimited data.

Hey, what about those 2G iPhone users? What happens to them? They are not affected by these plans at all, which only cover 3G data.

And new iPhone customers? They will not be able to sign up for the $30 data plan as of Monday. So if you add a line to your account? You're out of luck for that new iPhone.

What about iPhone customers who want to upgrade equipment? Surprisingly enough, there's good news there. You can keep your existing unlimited iPhone plan and migrate it to new equipment to upgrade or replace your handset, and even can renew your contract with that plan. However, when Apple introduces its new iPhone, it may offer new desirable plans at the same time. Bloom declined to comment on upcoming product announcements or special plans.

So, is the "iPhone plan" dead? The voice and texting plans remain unchanged. New iPhone users will be offered the $25/month 2GB plan instead of the current unlimited $30/month plan.

Why all the sudden raises in costs to consumers? Is it due to overtaxed infrastructure? "It's the opposite," said Bloom. "We're doing something [in introducing these plans] that isn't around at all. We're introducing a $15/month plan that will make smartphones available to whole new sets of consumers. It's much more affordable to them." Bloom explained that AT&T looked at typical data usage across the existing AT&T smartphone customer base. According to AT&T's research, about 98% of smartphone users consumed less than 2GB per month -- I did not get a separate statistic unfortunately for iPhone users. "We developed a plan that costs less than the $30 plan, where customers can use it comfortably with a fair and easy-to-predict structure if they go over their limits. I think there's a lot of value being added, consumers are getting what they need. For a vast majority of users they're getting that for less money per month." Bloom added that the AT&T infrastructure was not the driving force for the change, that the plans were developed according to historic usage data.

Are we going to see a MiFi-style option from AT&T? Bloom declined to answer, saying "I don't think that there's anything I can share on that topic."