At least in my experience--the support at OUP was great. There were a few things I did to help:
*Practice good tech support practices as a consumer.*
1. I noticed and reported via telephone any snags I encountered so that support would have a record of it.
2. I used telephone instead of e-mail.
They sent me an unencrypted set (so I didn't need any CDs or controversial software) when they couldn't solve the OED's incompatibility with my very strange confidentiality/personal encryption software. (PGP--99.9% of you do not use such things.)
A word, though:
For the majority of users, the OED will work just fine. OED v.3 is much improved.. it is actually a wonderful piece of software that acts exactly like M-W's software except with full-text search and wild cards, and excellent online help. Double-clicking on words is now supported, and you can press ENTER and get right to a definition--two of my pet peeves are now fixed.
The ability to run it off the hard drive means that it is fast and responsive.
If anything, C-dilla needs to clean up their act.. and provide better documentation to innocent engineers and support teams.
As long as you follow these instructions, you should be fine.
1. After installing and before launching the OED, insert your *data* CD (2.0 for the upgrade version, 3.0 otherwise.)
2. There will be a "Wait screen" telling you C-dilla is being installed.. it should go away automatically, and it will ask you again within 90 days.
It's really that simple.
And with world class support, how can you go wrong? 45 minutes of my time on the telephone gave me years worth of pleasure.. and as I said, I am a minority.