How do you get a user's name and description from their ID in the SDL Tridion Anguilla framework

I have written a GUI extension for SDL Tridion 2011 SP1. The GUI consists of an extra ribbon button and event handler which is triggered when a component is saved.

My event handler is registered as follows:

PowerTools.Commands.ItemCommenting.prototype._execute = function (selection) {    var item = $display.getItem();    $evt.addEventHandler(item, "save", this.getDelegate(this._onItemSaved));    $cme.getCommand("SaveClose")._execute(selection);};

and the event handler looks like this:

PowerTools.Commands.ItemCommenting.prototype._onItemSaved = function (eventitem) {    var comment = prompt("Please enter a comment", "");    $messages.registerNotification("Saving user comments...");    var commentitemid = eventitem.source.getId();    var commenterid = eventitem.source.getCreatorId();    var commenter = $tcm.getItem(commenterid);    var commentername = commenter.getDescription();    var commentdate = eventitem.source.getLastModifiedDate();    var commentversion = eventitem.source.getVersion();    //Call the service to update     PowerTools.Model.Services.AppDataServices.Append("ext:ItemCommenting", commentitemid, "<comment><user>"+ commenterid +"</user><message>"+ comment +"</message><datetime>"+ commentdate +"</datetime><version>"+ commentversion +"</version></comment>", null, null, null, false);};

This is working fine, except that the variable commentername is always undefined. Is there a better approach for getting the name and description of a user?

Additionally, does anyone know if the value returned by eventitem.source.getCreatorId() is actually the Reviser or actually the person who created the item?