Well, aside from having helped design, build, and fire several amateur and professional bipropellant pump and pressure-fed engines, no, not really :cyclops:
Hard starts are certainly a major problem with liquids, but one that is easily controlled with proper ignition sequencing, valve control, and purge systems. Proper propellant selection and modern computer control has simplified these issues dramatically. (This is one reason the System Solaire vehicle was such a disaster -- gasoline is a TERRIBLE choice for a liquid rocket propellant, largely because of the ignition challenges it presents.)
Maybe that's why I'm biased
Having worked on and fired many a liquid at the MTA, I can assure you it's not nearly as terrible as it may seem. If I can get a biprop together for a senior design project, it can't be too bad.
These guys have
over 5 minutes of firing on
their engine and they're a couple of hobbyists working out of their garage who bring up a dewar of LOX and a barrel of fuel in their truck when they want to fire. There is no real grand cryogenic propellant support system at the MTA, just a few test stands and a blockhouse. Biprops tend to crop up out there mostly because it's where all the biprop geeks hang out already -- there's lots of people to help you along.
And that's the valuable part, just like anything else: finding people to help you learn and find your way along the path. Like I said before, biprops aren't necessarily any more difficult or dangerous than a hobby hybrid -- personally I'd rather be around 60,000 gallons of LOX than 60,000 gallons of N2O any day -- they're just dangerous in a different way. Many people seem to see the "different" dangerous as "more" dangerous -- it's not, it just presents a different set of challenges to be aware of. And though TRF is certainly not the proper forum for the discussion of the design, build, and testing of a biprop engine, I think we can be a little more supportive and point out the proper place to discuss, rather than simply stating "biprops are dangerous, don't do them."