I started using Gsyncit a couple of weeks ago and so far, so good! I haven't noticed any lost contacts, but I backed everything up first before I used it in case something did go missing, which is only sensible if you're using any syncing software. I'm using it with both Outlook 2010 and on another computer Outlook 2007, and it works a treat on both syncing contacts, calendars, notes and tasks - finally!!
Admittedly, it's a little complex to set up the way you want it, but after six months of frustration trying to use the frankly useless HTC Sync with my HTC Desire HD, I'd rather have more options than fewer. I tried VCOrganizer before and had more stuff go missing with that, and it also took way longer to sync than gsyncit. True, you do have to sync up your notes via a third-party app, but I installed GDocs Notes and now everything is going swimmingly.
Also, Gsyncit supports multiple calendars, which means I can sync up my husband's calendar to see what he's doing (with his permission of course!) without requiring him to invite me to every appointment via Google Calendar which is what we were doing before. It's also much, much better than Plaxo which was a pain in the neck. My big headache has been duplicate contacts, but Google Contacts finds and merges them beautifully as long as you sift through your data first to get anything stray. That sifting took forever for me (I had 2500 contacts, but pruned out all the people who were dead or I didn't really know) but it was well worth it in the end.
I think this is a totally awesome app, and well worth the $19 to install it. I plan to put it on all three of my computers.