I always thought that the two are something real. Neji hasn't really been seen to react to Tenten negatively (at least from what I remember!) and Tenten seems to have real respect for Neji, and maybe even a small crush. How can you not say that her getting dolled up for his fight wasn't adorable? I see Neji and Tenten having a real friendship and even a mutual respect.
So what does everyone else think about this? And what do you consider to be the best evidence for the two?