It's a thread less than a half a year old and only one other answer, so I am going to respond as well. I had the same issue, especially with thinner parts.
The scraper tool supplied with the printer is slightly too thick to get under a part. I found that something like this:
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http://www.xacto.com/products/cutting-solutions/blades/detail/X218>
Called a #18 Heavyweight Wood Chiseling tool works really well to get under a corner. Once you start to get an edge up you can use any other flat tool you want.
I actually modified the scraper that gCreate sent and grinded the leading edge down to essentially create a giant version of the X-acto. But there are times I still use the X-acto blade because it is a thinner gauge metal which helps to keep the tool flat/level with the bed surface plane, and the edge is cut way sharper than my rough grind on the scraper.
It is important to use the width of the blade. Try to avoid using the corners, otherwise you can gouge the acrylic.