Widgets in WordPress themes are quite a nice feature, but nevertheless providing a style for most of them is a pain, as there are too many to apply a style for each of them.

Of course something like
after_title' => './h2..ul class="arrow".

and more is a nice deal, but the full control about the sidebar and its layout is lost, as any widget developer styles his work different: there should be some guidelines for the layout like use of h2 tags and so on.

But on the other hand where is the benefit except of making WP life easier? With the use of widgets the sidebar layout is totally different than the original theme: get back in control of your site, as with widgets enabled the widgets control the look and feel of your site.