Carl, yes indeed...but fortunately MK designed them intelligently so they are easy to handle.
Tread, thanks for the comments and support! I've gotten pretty comfortable with MKs and they've become a staple on builds the way some guys always use Fruils.
Marc, I think you've been spending too much time on your Enigma...you're starting to hear things!
Steve, it is more work, no question there, but the payoff comes in the end in terms of weathering and handling for installation. As you've discovered, working withe one-piece tracks for "dead" track design vehicles is always a challenge. Workable sets overcome that, allowing you to tailor your sag accordingly. This is even more flexible when you have a kit that includes adjustable idler wheels (and some MK sets include parts to allow you to adapt mounts to be adjustable as well depending on the "host" kit you're working with).
MK stands for Modelkasten, they are a company in Japan that produces the sets (among other things). Here's their home page (it's in Japanese, so Google Translater will help). http://www.modelkasten.com/ As far as quick Pros/Cons...here goes:
Pros: Styrene links, no special glue required to assemble, produce workable track runs, sets include spare links/pins, can be painted using standard model paints/methods, not kit-specific, wide range of tracks available for different vehicle types (1/35 scale), cheaper than metal tracks (depending on supplier/source, I use www.rzm.com for all my MK track needs).
Cons: More fragile than metal tracks, time consuming assembly process, sensitive to "hot" paints like lacquers, some clean-up required depending on set in question, not ideal for "live" track types (i.e. Sherman tracks).
HTH!
Eric, separate guide horns add a little bit to the assembly time but not very much...and you can't argue with the in-scale result!