The link below is selling the 100 lapper for $179. Here are my thoughts on the product. I've had mine since June.
1. Pretty accurate. GPS technology is sound.
2. The GPS thing goes on your upper arm and although it's not heavy, you look like one of those jogger types with a MP3 or CD player on their arm.
3. The pace function has a few seconds delay... so the pace it shows is the pace you were running about 5 seconds earlier. A little confusing when you're doing pick-ups and you look down and it reads 7:05/mi when you've already picked up the pace.
4. In very cloudy/rainy conditions you can lose the GPS signal. I've only lost it for a few seconds and then picked it up again. For measurement purposes, the Timex thing assumes you run in a straight line (shortest possible distance) during the time that you've lost the signal.
5. I've also read that you can lose the signal if the GPS thing doesn't have a clear view of the sky. I've run in some pretty wooded areas without a problem, though.
6. Replace the battery when you get the low battery warning... you've only got about 30 minutes left once that happens. It seems you need to replace the battery every 10 hours or so.
7. I can't figure out how to store the data from each run. In my regular Timex Ironman watch I can store lots of runs. I cannot determine if the Timex Speed+Distance has this capability. So I have to clear the data from my last run before I start my next run. It doesn't have a hook-up to a PC or anything to download the data, either. You've got to write it down, or it's gone.
8. Overall, it is very consistent (only off by a couple of hundreths or so). You can switch between metric and English readings.
9. If you want to use it to measure off a mile or something for intervals, you should run for a couple of miles first, then measure your interval. It seems that it takes a couple of minutes to get a good signal.
Good Luck with your decision. I like mine, and use it to measure new courses.