We're planning on upgrading our heavily customized 2.17.4 version of
Bugzilla to a more recent version and I'm looking for your experiences
with 2.18.X and 2.20.X as well as your suggestions about which version
we should upgrade to.

Have you found 2.18.X to be very stable (fairly bug-free)?

How about 2.20.X?

We tried to make use of the "Custom Field" patch that is available and a
previous employee here installed an incomplete version so we have it
partially working. Has the patch been upgraded to work with these two
versions? Is it complete (can you do advanced queries on Custom Fields
without getting the Internal Server error)?

Thanks for your consideration.

Steve Blumenkrantz