When you install Visual Studio SDK on Vista, it doesn't install by default on X:\Program Files, but on X:\Program Files (x86).
Instead of moving things around I created a symbolic directory link:
mklink /D "Visual Studio 2005 SDK" "c:\Program Files (x86)\Visual Studio 2005 SDK"
Works like a breeze!
When you add a custom field type that can hold more than the 255 characters you can't use a field of type SPFieldText because it has a max length of 255 characters.
An obvious candidate is to use the field type SPFieldMultiLineText. No problems so far. But... in your custom version of the fldtypes.xml file (for example fldtypes_mytypes.xml) you have to define your parent type of the custom field. You would expect a parent type named MultiLineText, but no, that would be too obvious. It should be Note. Not documented, such a pity...
<?xml version="1.0" encoding="utf-8" ?>
<FieldType> <Field Name="TypeName">LongText</Field>
<Field Name="TypeDisplayName">Long Text</Field>
<Field Name="TypeShortDescription">Long Text</Field>
<Field Name="FieldTypeClass">...full qualified class,assembly name...</Field>
A link with some more info (in Spannish): http://www.ideseg.com/SharePointDestripandoElWiki4.aspx