Maybe we should decide to use tables or h5py and stick with one or the other:

https://code.google.com/p/h5py/wiki/FAQ#What%27s_the_difference_between_h5py_and_PyTables_?
http://www.pytables.org/moin/FAQ#HowdoesPyTablescomparewiththeh5pyproject.3F

for our purposes they appear similar, with pytables maybe a bit better on performance but h5py being simpler to use. Thoughts?