I downloaded it 3 times so I hope it's good
Where did you get the update from specifically? I know on the XDA developers forum, there is one thread in the Q&A forum about the cheesecake updates for 2.3.5 with 4 different builds. I found that I had to download that directly within my browser on my phone. If I downloaded it to my computer and then did an SBF PUSH or copied it via USB Mode, it didn't work.
However, my issue now is, WiFi is messed up with the 2.3.5 update. It keeps cutting out every few minutes which is not acceptable as it interrupts large downloads. I have yet to find an answer to this issue and there are others experiencing it as well.
I've sbf'd 2.3.4 and reactivated my phone at LEAST 15 times this past weekend and I'm sure I'll be getting a phone call from Verizon wanting to know why I've activated my phone so much!
But, I digress. You don't have to root to update the 2.3.5. In fact, you should hold off on doing that until you get 2.3.5 to successfully apply itself, but test your WiFi by downloading large files to ensure it doesn't cut out. It usually lasts about 2 or 3 minutes, then it drops and re-establishes itself. Then, 2 to 3 minutes later, the vicious cycle starts again with it dropping and starting back up.
No one seems to be able to determine what the issue is since it doesn't affect everyone, but it does seem to be affecting quite a lot of X2 owners out there, me included.