200 Hour CRM Conversion

We just finished up a conversion for a client from MS CRM 3.0 to CRM 4.0.  Over 200 hours and 9 months of time have passed since we began the conversion.  What was the problem?  The largest problem was that the database schema had been altered.  Various custom indexes were added and some referential constraints were removed leaving a mess of  not only the schema, but over time, the data.  I am sure the changes were well – intentioned but disastrous to a succesful , timely upgrade.  All in all over 30 attempts were made.  It was an interesting trip and learning experience but the moral of the story is simple …. If you plan on upgrading CRM (or any other product) … stay within the best practices guidelines.  If you need more than what that offers … then document everything you do!!