Apparently, from what I've been able to gather (without attempting to create an account at Lightning Source), is that LS has effectively closed it's doors to self published authors with fewer than a certain number of books. Prior authors, with books currently in their database or an account in the system are grandfathered it.
Still, I know of at least two authors in the past few months who were able to get approved, but know many more that were redirected to Spark by a representative.
Spark is their alternative for those authors, but without all the bells and whistles. For example, I believe that you only have the option to set your discount between 40-55%. On LS, you could set your discount to 20% and most online retailers would or could pick you up. You wouldn't be able to get into stores (if they even wanted the book) in most cases with that low of a discount.
A lot has changed in the past few months. Last time I checked all titles were locked at 55% and returns were not possible. Both these terms have changed.
On top of the $49 fee, there are other costs involved. You must have your own ISBN, and those aren't cheap. I think, if your goal is to get into bookstores (the odds are not in your favor), then Spark would be the better option just because it doesn't have the 'taint' of being connected to Amazon/Createspace. Also, createspace books are non-returnable, they will usually only be ordered by request of a customer at a local bookstore.
If you have your own ISBN, then you could always start out at Createspace, where it's free (minus the proof copy) and if you sell a lot of books you could then take that ISBN and branch out, so to speak.
