Pros: Carry your Microsoft Outlook meetings, contacts everywhere. Get meeting alerts.
Cons: Clumsy interface to appointments is also a little buggy.
Please also read the excellent review by arinkent, which has broader scope in its coverage. This review focusses on a couple of the more irritating issues with the watch.
Why I need the Datalink
I found I was missing meetings. I don't carry my pocket PC in my pocket, because I usually don't have a shirt with a pocket big enough to hold it in its protective cover. A watch synced to Outlook seemed like the perfect answer. And overall, this watch is your ONLY choice if you want your outlook calendar + contacts on your wrist. (The Fossil wrist palm PDA is (IMHO) too big and too fragile to be a viable watch.)
The watch has kept me on-time for meetings. This has been invaluable, but it has some very annoying quirks.
1) When you import recurring appointments from Microsoft Outlook, the watch displays them ordered by the first date of the recurring meeting (which is usually months ago). This results in the user scrolling through appointments on the watch and they are in no special order - Monday may come after Tuesday which may come after Friday, just depending on the original start date of the recurring appointment. This makes the viewing function pretty useless. (But the alarm function works fine - you find out when the meeting occurs, you just can't effectively review them in advance from the watch.) Timex needs to get the watch to display the future date/time recurring meetings will occur. (Non-recurring meetings work fine.) My solution to this problem has been to manually edit each recurring appointment to give them an artificial start date which results in them appearing in date order, but this obviously defeats the "automatic import" feature.
2) The cable is challenging to attach. The user has to hold the cable between thumb & forefinger, which puts the thumb in conflict with the watchstrap, and the 4th finger is used to operate the latch. This is difficult, and could have been easier.
3) The strap is not replaceable. I'm worried about what happens when it wears out.
4) Some appointments which are created from meeting invitations (importantly, from one particular outlook site) get imported offset by 5 - 8 hours from the actual meeting time. They are correct in outlook, but wrong on the watch. This may be an outlook version issue, but is a trap.
5) The terminology used in the GUI is non-intuitive. Specifically, "import into mode" seems to be the term used to mean "import data from outlook".
I do like getting an alarm when a meeting is about to begin, and I do like having my contacts on my wrist. However, there are significant issues with the Outlook integration. This may or may not be a deal-breaker for you. In my opinion, the issues are workable but annoying.