Is it possible to style a Spark Button like an old Halo Button? (with CSS only)

I think Adobe are messing with me, from all the docs and tutorials it seems like styling a simple button got much more difficult in Flex 4 (Spark). I used to be able to have my designer create the CSS as it wasn't too far off from web standard CSS. Now it seems like I need to make a skin first as outlined in this post?

Below is the old button style.

Button {
    fontFamily: "Arial, Helvetica";
    fontWeight: bold;
    fontSize: 11px;
    paddingTop: 0px;
    paddingBottom: 0px;
    highlightAlphas: 0.42, 0.13;
    fillAlphas: 1, 1, 1, 1;
    fillColors: #B9DEF8, #9AC3EB, #B9DEF8, #9AC3EB;
    color: #477199;
    textRollOverColor: #477199;
    textSelectedColor: #3399cc;
    borderStyle: none;  
}

thanks!

Skinning the Spark Button would be a programmatic approach to which you could mimic the Halo mx:button very closely.

If you just wanted your application to use the Halo theme, you could use Halo theme.

It's also important to note mx:Button included things like icon, which Spark Button does not.

As you denote you want to use CSS only, you'll have to dive in to mx skin class at:

mx.skins.halo.ButtonSkin

Spark theme:

Halo theme:

Based upon your CSS for spark:

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
               xmlns:s="library://ns.adobe.com/flex/spark"
               xmlns:mx="library://ns.adobe.com/flex/mx"
               minWidth="955"
               minHeight="600">

    <fx:Style>
        @namespace s "library://ns.adobe.com/flex/spark";
        @namespace mx "library://ns.adobe.com/flex/mx";

        s|Button
        {
            fontFamily: "Arial, Helvetica";
            fontWeight: bold;
            fontSize: 11px;
            paddingTop: 0px;
            paddingBottom: 0px;
            highlightAlphas: 0.42, 0.13;
            fillAlphas: 1, 1, 1, 1;
            fillColors: #B9DEF8, #9AC3EB, #B9DEF8, #9AC3EB;
            color: #477199;
            textRollOverColor: #477199;
            textSelectedColor: #3399cc;
            borderStyle: none;  
        }
    </fx:Style>

    <s:VGroup width="100%"
              height="100%"
              paddingTop="10"
              paddingLeft="10">

        <s:Button label="Hello, world!" />

        <mx:Button label="Hello, world!" />

    </s:VGroup>

</s:Application>