Not to divert you away from a watch, but have you considered using a cell phone (if you have a smartphone, that is)?  I was looking into watches as well but found that with the many free and cheap app options out there, and a cheap armband to hold it, I was able to use my phone instead.  Although I am fairly new to running (only running 3 miles 3x a week), I still don't see needing to spend hundreds on a watch even if I was running a lot more.  I believe there are Bluetooth HRM out there for use with your phone, too. 

Again, not trying to steer you away from watches, but thought I'd throw this alternative to you in case you hadn't thought about it.

I use the Garmin 405 with the heart rate monitor. The watch tracks everything you need to provide you all the information you need to improve your running performance. The software which you install on your computer allows you to sync the results stored on he watch to the program. The program also allows you to enter your age weight and to better calculate calories burned and max heart rate. A smart phone will not do that. Both the software and watch are extremely customizable and allows you to set up the information you want. There is a reason Garmin is a leader in GPS technology.

The Runkeeper app lets you choose how often you want to hear your updates.  They can be distance based or time based so you could have it update you every 1/4, 1/2 mile of every minute if you wanted.  I have some serious technology envy over the Motoactv, but I can't justify the expense when I have a solution that works just as good. 

Personally I sweat too much during a run to carry a phone that costs $700 to replace. I used a Garmin Forerunner 305 for awhile but the battery life was only about 12 hours and it wasn't waterproof. Not much good for doing an Ironman unless you typically win your age group and don't want to swim with it on. Then I bought a Garmin 310X to use in conjunction with my power meter hub on my bicycle. They're pretty much the same in size and thus similarly uncomfortable. The Forerunner 310x has a more comfortable band and is good for 18 hours. The problem I had with both watches is that they're basically just workout watches. Garmin products I've also found are not that intuitive and very intense to program. Plus you can't just wear them everyday to tell time. So I sold the 305 and the 310x is now collecting dust.

Recently a friend gave me a Timex Ironman Run Trainer S and D with Heart Rate Monitor (ITEM # - T5K575F5). I also have the cadence foot pod. OMG is this thing nice, comfortable, and easy to use. I wear it as a daily watch then turn on the GPS when I run. I charge it about every 3-4 weeks. It's as easy to program as any Timex Ironman watch and it's waterproof.

I would highly recommend looking into this watch.

I have the Nike+ GPS watch and it is amazing.  It tracks all the necessary information while I run and then I plug it into the computer to use the Nike+ software.  I absolutely love it and it has been a real motivator for me!