This worked for me on CE 1.8.1. It's based off Shein's answer, and addresses the wrong option getting selected on load. I basically just copied/pasted the Product.Config.fillSelect() method from /js/varien/product.js. Within the pasted code I changed:
element.options[0].innerHTML = this.config.chooseText;
to
element.options[0].innerHTML = element.config.label;
This allows keeping product.js unmodified, and just override the method. The only drawback is any future core updates to that method will need migrating.
Since the new code just gets the "label" setting, the data-choose-text attribute on isn't needed on the select tag
<?php
$_product = $this->getProduct();
$_attributes = Mage::helper('core')->decorateArray($this->getAllowAttributes());
?>
<?php if ($_product->isSaleable() && count($_attributes)):?>
<dl>
<?php foreach($_attributes as $_attribute): ?>
<dt><label class="required"><em>*</em><?php echo $_attribute->getLabel() ?></label></dt>
<dd<?php if ($_attribute->decoratedIsLast){?> class="last"<?php }?>>
<div class="input-box">
<select name="super_attribute[<?php echo $_attribute->getAttributeId() ?>]" id="attribute<?php echo $_attribute->getAttributeId() ?>" class="required-entry super-attribute-select">
<option><?php echo $_attribute->getLabel() ?></option>
</select>
</div>
</dd>
<?php endforeach; ?>
</dl>
<script type="text/javascript">
Product.ConfigDefaultText = new Class.create(Product.Config, {
fillSelect: function (element) {
var attributeId = element.id.replace(/[a-z]*/, '');
var options = this.getAttributeOptions(attributeId);
this.clearSelect(element);
element.options[0] = new Option('', '');
element.options[0].innerHTML = element.config.label;
var prevConfig = false;
if (element.prevSetting) {
prevConfig = element.prevSetting.options[element.prevSetting.selectedIndex];
}
if (options) {
var index = 1;
for (var i = 0; i < options.length; i++) {
var allowedProducts = [];
if (prevConfig) {
for (var j = 0; j < options[i].products.length; j++) {
if (prevConfig.config.allowedProducts
&& prevConfig.config.allowedProducts.indexOf(options[i].products[j]) > -1) {
allowedProducts.push(options[i].products[j]);
}
}
} else {
allowedProducts = options[i].products.clone();
}
if (allowedProducts.size() > 0) {
options[i].allowedProducts = allowedProducts;
element.options[index] = new Option(this.getOptionLabel(options[i], options[i].price), options[i].id);
element.options[index].config = options[i];
index++;
}
}
}
}
});
var spConfig = new Product.ConfigDefaultText(<?php echo $this->getJsonConfig() ?>);
</script>
<?php endif;?>