These are probably my contenders:

• UltraTax.  Superior software, but more expensive.  It is worksheet-based, so there is a big learning curve.
• Drake.  The best customer support around and costs less than ProSeries.  Decent software, but the 'flow' takes some getting used to.  I also don't like that you can't see the automatically calculated fields (such as depreciation) directly on the worksheets (you need to go elsewhere to see what those numbers actually are).
• TaxAct Professional.  Entering data is very similar entry to ProSeries and the software costs noticeably less.  However, (a) it is slightly less automated than ProSeries, (b) is released until much later than ProSeries (but ProSeries is pretty much useless for the first two months anyways), and (c) is still based off of Do-It-Yourself software (TaxAct for consumers, likewise ProSeries is TurboTax based), so the company's priority is towards the consumer version.
• ATX.  Similar to TaxAct.  Data entry is a bit more annoying, but it is made from a company that focuses on tax professionals, rather than Do-It-Yourselfers.