... speaking of which, I am also considering technology lifecycle. Once you start tagging your collection, it is a massive amt of work that you put into it, and definitely you don't want to lose it. Both Lightroom and ACDSee and Picasa will create a fairly large DB (2-4 GB for each fo the above mentioned sw, in my case) including thumbnails and metadata.
Now, in this specific regard, I'd feel safer that Lightoroom will survive for years, and should it ever disappear, it is so widely and professionally used that converters to extract data from its db to be migrated somewhere else will likely be available when needed.

But, how about ACDSee or Picasa. How unlikely is it that Google or ACDSystems just stop development at some point in the future and you're left with an outdated software and its huge locked proprietary db?
Maybe I'm paranoyd or as usual looking for the non-existent definitve tool, but from this perspective Lightroom makes me more comfortable.

Still, as a product, ACDSee is the closest to what I personally want and like.