Personally, I found the "retirement visa" quite easy to do. The paperwork was fairly simple, straightforward and easy to do.

Marriage visa stuff - has also changed a little bit in terms of being more stringent about meeting the requirements and documenting the marriage. By far the best place to get advice is:

Thailand Forum

It's where I go every year a few months before it is time to renew whatever visa I am on at the time - just to check and see if there are any changes or complications. People there are quite helpful. However, it is like any online forum, you do have to sort through the barstool experts to get to the people who really know and have experience with it.