Hi,
I started a submarine build last nite. My intent is to paint it light/med grey over white and add the shark mouth decal shown below. 
So far its been a really quick build, since there are not many parts, but I did run into a couple small issues (mostly due to my not following the instructions correctly and also because I'm not necessarily as good a builder as others here).
The biggest issue on the kit for me was that it has some very fine railing molded separately that goes on the side of the sail. The pieces were only about 0.5 mm thick (at most). They were molded with very small legs that were supposed to fit into holes on the sail, but the sprue connections were not on the legs, but rather the thin railing itself, which made cleaning that area up a bit difficult. In addition the holes in the sail seemed potentially a bit undersized.
After trying to clean and attach them for a while, I ended up accidentally breaking them and loosing a couple sections into my carpet. As such, I ended up removing the pieces that I had attached and replacing them with some 0.9mm PlasticStruct rod that I had.
The other difficult part was that some of the periscopes and antenns are very thin and meant to fit into holes in the top of the sail, that seemed to be a bit too small for them. In addition, the locator pins on the bottom of the masts/antennas etc were also less than about 1mm deep or so, so that they really didn't give a lot of connecting surface or help in making sure that the mast/etc was mounted straight.
Other than that though, I've got the model mostly primed and hope to start painting it soon 
Pat