This retailer's web site has some info on the changes for the W3037:

http://www.designerappliances.com/miele-w3037.html

They are saying less water and energy use on the normal cycle, better shock absorbers for the drum, better quality control on the panels, and improved drum lighting. They make no mention of which is the additional wash program.

The reduced water and energy consumption improvements over the W3033/35 correlate to what is listed in the washing machine ratings published by the US government.

As for the other changes I have not been able to find another source that confirms the information.

I have a W3033 and it definitely does have the "custom" program wash cycle option.

Because there were some improvements made, I decided to go with the 3037 and ordered it today. We have been without a working washing machine for 7 weeks so I am very eagerly anticipating the arrival of the new Miele : )

Thank you very much for your help, ZoapBox and cryptandrus!

The difference is that the drum of the W 3037 is larger. Its gone from 54 litres to 59 litres in volume. Don't know how this translates to cubic feet. This model also has 3 shock absorbers instead of 2.

Once you get the machine and try to use it you may also find this helpful.

Any energy improvements in the Normal program are nice but it's basically the machine's default cold-water program since it doesn't use the heater.

Here is a link that might be useful: Miele Washer Cheat Sheet

Thanks mr_wash and rococogurl.

rococogurl: The cheat sheet looks incredibly useful - I have already posted a copy on the inside of a laundry room cupboard. Thank you so much for the link and for compiling all of this information!

Yup, use my cheat sheet all the time :)