Are you asking LEGO purist this question or brickfilmers in general?  LEGO purist will complain about it, but not all brickfilmers are LEGO purist and not all brickfilmers will care what medium you use as long as it is brick plastic construction toys.

Do what you got to do.  All we care is the finished film, be it made up of half LEGO, half Megablok, KREO, CG bricks, etc.

I'm not a pourist. I'll use anything that makes my film better and completes the set the way I want to. It's ok to do this as long as you're happy with it pal.

First, spending $20 on something that will only be in one shot is probably not the best use of your money.

If you're planning on using it and/or most of the parts later, then go ahead. But remember that the quality will be noticeably lower. I can't find any recent reviews of Enlighten stuff on Eurobricks, but here's one post that may help:

(Keep in mind that the above post is now over a year old, and a lot can change in a year.)

Going off of that, it sounds like an OK deal, even if I am (Generally) a Lego purist.
And one final thing, shipping from Hong Kong WILL take close to an eternity. So be sure to order it far in advance.

Why not create a design for a train carriage (or use an existing design) and buy the bricks you need for it off Pick A Brick or Bricklink?  That way, you've got exactly what you want in terms of design, at a convenient price, made out of official LEGO bricks.

I just bought a "Best-Lock" set the other day. Definitely poor quality, had to glue a few pieces together, but I don't plan on ever taking it apart and it gave me some valuable props for cheap. No complaints so far.

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