I would just use the MultiProperty for CMS 5. That way you don't have migrate the existing property data over to the LinkItemCollection. Sure if the LinkItemCollection had any features that the MultiPageProperty diden't have, and that you needed now, but at the moment they are both pretty similar (feature wise I think the MultiPageProperty still is a little ahead).

Thanks for your input. Does it work in CMS 5 R2? The requirements on coderesort include CMS 5 R1.

I've had no problems using it with EPiServer CMS 5 R2, don't remember if I had to recompile it though.

Does anyone have any suggestions when upgrading a CMS 5 site to CMS 6?

We have replaced the MultiPage property with LinkCollection on several sites. As they share the same data structure it is really not a big problem. There can however be issues with data being lost in the migration processes, but we got around it by changing the property type first back to a standard XHTML string property and then to LinkItemCollection after the migration/upgrade is complete. Both these changes was done by running a SQL UPDATE query directly against the tblPageDefinition table.