I have a set of users in my SharePoint site with a few custom properties like GUID, LOS, YOS etc. My application needs to access the user custom properties and do CRUD operations on the properties. I have searched in the net but I found only how to access basic properties like email, name etc. Can anyone let me know how to accomplish this using client object model of SharePoint 2010?
Client Object Model is bound to SiteCollection scoped functionality. The reason you can only get default properties is because Custom Properties are not synced to the UserInfoList in the SiteCollection. With Client OM you are not able to get the UserProfiles the way you should when building a Farm Solution for instance.
If you do need to use Client OM because this is hosted in Office 365 I'm afraid the only option is to put the custom properties in a custom list somewhere in your SiteCollection with a reference to the users they're for.