I thought I read somewhere that the LED tail lights can only be seen well if viewed from straight on, so if you look at them from an angle (like the next lane) you can't see nearly as well as standard bulbs because the LED's are directional.
Half-true! Most LED's have a narrow field of light dispersion, to focus maximum brightness/intensity. You can, however, get some wide-angle LED's that are quite bright (think modern Caddy taillights, etc.). It all depends on your needs and application.... but, if you have a stock taillens that should help disperse the light enough for angled view, but focus it where you need it most- at the clown behind you in his honda with a wing :) Many LED's are so cheap, that experimenting to find your right solution won't cost you more than a $20 anyway!