Upgrading from ExpressionEngine version 2 from version 1 - why?
Over the years we have build countless sites in ExpressionEngine and a lot of them were built in the first version of the software. After many years of construction EllisLab finally released version back in January 2010, oh how time flies, it doesn’t seem long ago at all!
This begs the question if you have client sites running version why would you upgrade?
E-commerce can still be done with version 1 but with the powerful e-commerce options such as Brilliant Retail and Store only running on version 2 then if you are thinking of adding even a small store to an EE1 site then it's a good idea to update to version to to utilise these fantastic options.
Improved User Interface
Version 2 has a far improved user interface and is a lot easier to sue for clients than version 1. It's relatively similar with the top navigation but it's enhanced from version 1.
Vastly larger choice of Add ons
There is a much bigger choice of add ons for version 2, just about all developers build new add ons for version 2 and discount the first carnation.
If you require support from the forums for EE1 then i'm afraid it doesn’t happen anymore. From april 2012 EllisLab stopped official supporting it. With he forums generally and for EE2, once you have build up a lot of experience building EE sites then you certainly don’t, well in our experience visit the forums much anyway, but from time to time it can be handy with many other devs and their official team their, but its in just about all cases third party support we need and that is found on Devot-ee or GetSatisfaction or Solspace forums.
Version 1 was deprecated and replaced for one main reason, that was allowing the product to be extended thoroughly with being powered with CodeIgnitor, EE 2 just runs faster and with the performance add ons only available in EE2 makes it a newer, improved on and just better product for performance.
If the client is on a very low budget and there is no more updates and features planned to be carried out on their version 1 ExpressionEngine then you can leave it unattended. A good idea here is to have a maintenance contract in place that allows for upgrades to take place. Generally we charge 2 days time throughout the year to keep them updated 3 times a year which should take in security upgrades.