For the time being you can use the following workaround:

CSS:
	<style>
		.RadForm_Bootstrap.RadForm.rfdButton form a.rfdSkinnedButton {
			padding: 0px;
			height: 32px;
		}
			.RadForm_Bootstrap.RadForm.rfdButton form a.rfdSkinnedButton input.rfdDecorated {
				height: 32px;
			}
	</style>

ASPX:
		<telerik:RadScriptManager ID="RadScriptManager1" runat="server"></telerik:RadScriptManager>
		<telerik:RadSkinManager ID="RadSkinManager1" runat="server" Skin="Bootstrap" ShowChooser="true"></telerik:RadSkinManager>
		<telerik:RadFormDecorator ID="RadFormDecorator1" runat="server" DecoratedControls="All" />
		<asp:Button ID="Button1" Text="Click" runat="server" />