How are you actually handling commission calculations at 25-100 reps?

I've been talking to a few sales ops people and I keep hearing the same thing all the time like somewhere between 25 and 100 reps (not many), commission management turns into a chaos, but the current tools like xactly, SAP, Spiff feel too complex and super expensive, sometimes does not make sense to use those tools because I will end up paying more money than the incomes the company sales.

So I'm curious what people here actually do day to day

• What do you use right now to calculate commissions, spreadsheet, a tool (which one), or a mix?
• If it's spreadsheets, what's the part that actually hurts? multi-currency? quota changes mid-period? splits? month-end reconciliation?
• If you tried a commission tool and went back to Excel, why you go back?
• Roughly how many hours a month does the whole commission process eat, and who eats them?
• Has a commission error ever blown up into a dispute with a rep? How do you manage that?

I am trying to understand how bad this really is and how people cope.