For the time being the following workaround can be used:
		<script>
			function OnClientClicked() {
				alert('OnClientClicked');
			}

			function OnClientClicking() {
				alert('OnClientClicking');
			}

			function fixBtnClicked(sender, args) {
				sender._useModules = false;
			}

		</script>
		<telerik:RadButton ID="RadButton1" runat="server" ButtonType="LinkButton" Text="Click" OnClientLoad="fixBtnClicked" Target="_parent" NavigateUrl="http://www.google.com" OnClientClicked="OnClientClicked" OnClientClicking="OnClientClicking" />

For the time being you can use the following workaround:
JavaScript:
		<script>
			function fixBtnRepaint(sender, args) {
				sender._useModules = false;
			}
		</script>
ASPX:
				<telerik:RadButton ID="RadButton1" runat="server" Text="Click" OnClientLoad="fixBtnRepaint">
				</telerik:RadButton>

 For the time being the following workaround can be used:

ASPX:

       <telerik:RadButton ID="RadButton1" runat="server" Text="Click" NavigateUrl="http://www.google.bg" Target="_blank" ButtonType="LinkButton">
        </telerik:RadButton>
        <script>
            Telerik.Web.UI.Button.NavigationFunctionality.prototype._handleNavigateUrl = function () {
                $ = $telerik.$;
                var that = this,
                    target = that.options.navigateTarget,
                    url = that.options.navigateUrl;

                if (target && target == "_blank")
                    window.open(url);
                if (target && target == "_parent")
                    window.parent.location.href = url;
                if (target && target == "_top")
                    window.parent.location.href = url;
                else if (!target || target == "_self")
                    window.location.href = url;
                else {
                    var targetFrame = $("iframe[name='" + target + "']").get(0)
                                        || $("frame[name='" + target + "']").get(0)
                                        || $("#" + target).get(0);

                    if (targetFrame && targetFrame.tagName.toLowerCase().indexOf("frame") > -1)
                        targetFrame.setAttribute("src", url);
                }
            }
        </script>

Currently the default height of RadButton with Silk skin and CssClass="rbPrimaryButton" is 28px. The correct height must be auto, so that the text inside the RadButton can be wrapped when it is longer and no height is specified. For the time being the following CSS workaround can be used:
CSS:
        span.RadButton.RadButton_Silk.rbLinkButton.rbPrimaryButton {
            height: auto;
        }
ASPX:

            <telerik:RadButton ID="RadButton1" runat="server" Skin="Silk" ButtonType="SkinnedButton" Text="aaaaaaaaaaa bbbbbbbbbbbbbb cccccccccccc" Width="200px" CssClass="rbPrimaryButton" />
            <telerik:RadButton ID="RadButton3" runat="server" Skin="Silk" ButtonType="SkinnedButton" Text="aaaaaaaaaaa bbbbbbbbbbbbbb cccccccccccc" Width="200px" CssClass="rbSecondaryButton" />

Declined with the reason:

Item is a duplicate of http://feedback.telerik.com/Project/108/Feedback/Details/127356

 Currently the value of RadButton's property 'Width' is not applied correctly and its width is not as specified.

A workaround is using ButtonType=SkinnedButton or using the Glow or BlackMetroTouch skin.
You can use the following CSS workaround to remove the additional opacity Safari adds for the input that results in the sprite being visible:
        .rbDisabled .rbDecorated {
            opacity: 1;
        }

For the time being the following JavaScript workaround can be used:
JavaScript:
		function pageLoad() {
			fixImageURL();
		}
		function fixImageURL() {
			var imageBtns = $telerik.$('.rbImageButton');
			for (var i = 0; i < imageBtns.length; i++) {
				var btnStyle = imageBtns[i].getAttribute('style').replace("background-image:url(", "background-image:url('").replace(");", "');");
				imageBtns[i].setAttribute('style', btnStyle);
			}
		}
ASPX:
		<telerik:RadButton ID="RadButton1" runat="server" Width="50px" Height="50px">
			<Image ImageUrl="50x50.png" />
		</telerik:RadButton>
		<telerik:RadButton ID="RadButton2" runat="server" Width="50px" Height="50px">
			<Image ImageUrl="50x50.png" />
		</telerik:RadButton>

For the time being the following workaround can be used:

CSS:

    <style>
     .RadButton.RadButton_Metro.rbSkinnedButton:focus input.rbDecorated {
            background-color: #25A0DA !important;
        }
    </style>

        <telerik:RadSkinManager ID="RadSkinManager1" runat="server" Skin="Metro"></telerik:RadSkinManager>
        <telerik:RadTextBox ID="RadTextBox1" runat="server"></telerik:RadTextBox>
        <telerik:RadButton ID="RadButton1" runat="server" Text="click" />