Now that you have saved your pennies and cashed out all of your sales to buy that lens you have been saving for, don't skimp on the filter. That is if you use filters. Photography is not a cheap hobby, and now that you've spent your hard earned money on a good lens do not ruin it by putting a $20 filter on it.
I found myself doing this, and couldn't figure out why my images weren't as sharp as they were suppose to be. I am ashamed to admitt that it took me a couple weeks and several tries to figure this out and I now spend more on filters than I paid for my 1st lens.