Microsoft Dynamics (Axapta) upgrade

I'd like to upgrade Axapta from version 2.5 to 3.0 or 4.0 (to be considered). Probably it wouldn't be so hard, but my version has A LOT of customized code - new classes, data sources, forms, etc. and I have no idea how much time can it take. Do you have any experience with upgrading from 2.5 to 3.0 or 4.0? How difficult may it be to move or rewrite all changes along with new Axapta version? I'll be than开发者_如何学编程kful for any kind of help.

Fist off, I wonder why you consider to upgrade to Axapta 3.0 (from Oct 2002) or Axapta 4.0 (Mar 2006), when there is newer alternatives like AX 2012 available right now.

Element types

Generally new elements (forms, classes etc.) poses only minor problems when upgrading. Modified elements are much more time consuming. Data structure changes may also pose challenges as it may require rewrites. Reports may be very time consuming to upgrade. A total rewrite of an element should always be considered, it is sometimes faster.

Compare process

The upgrade process for an individual modified element is usually straightforward when you use the compare tool (twice). Compare your old layer with old original layer, and compare new layer with new original layer. The modifications should match more or less.

Estimation report

AX 2009 provides an estimation report located in Tools\Development tools\Code upgrade\Estimation report. The time estimate is based on an estimated average time to upgrade certain code conflicts (setup in the parameters).

I have no prior experience with the report, but the any estimate is uncertain with 50% at least.