To add to what Eddie has said - Polar Lights is a now-defunct company that was part of the Praying Mantis corporation. Sadly, Praying Mantis was bought by RC2 (Racing Champions) who wanted the Johnny Lightning line of Die-cast vehicles. They also bought out AMT/ERTL some years back, mostly for the ERTL Die-cast line.
Polar Lights is basically now a brand-name part of RC2 - and RC2 has announced that they're doing away w/that name brand, tho should be continuing w/the Star Trek line for as long as they've got the license from Paramount. Last scuttlebutt I heard was that RC2 is negotiating to continue the Trek License, so we should see their kits for a goodly while.
To answer your second question - the PL brand kits all have their quirks, but are generally much better engineered than most SciFi kits from major manufacturers. They were also engineered w/the modeler in mind. The 1/1000 scale TOS 1701 kit, for example, is very lighting friendly w/it's two-part warp nacelle pylons, as well as a number of clear parts. Their Klingon D-7 kit had a problem w/the initial run in that the neck pieces didn't fit quite right forcing the builder to either scratchbuild a shim for one part or to build the kit w/the entire neck/head assembly canted to one side. Polar Lights fixed that right away, however, and later releases of the kit were corrected.
The only negative I can say about Polar Lights/RC2 is that they have pretty much ZERO customer service when it comes to missing parts in a kit. If you purchase one and it's missing part(s) you can't send it back to them, get them to send the parts or get a refund from them on the kit. They'll tell you to take the kit back to where you purchased it and ask for an exchange or refund. Gone are the days when you could call up ERTL, tell them of a missing part, decal sheet or whatever and get a replacement mailed to you for free. ![Sigh [sigh]](/emoticons/icon_smile_sigh.gif)