To make a change from the raft of complaints about transfer companies I thought I would write up two recent positive experience instead.
Alpybus - travelled with them both ways in March. Driver was great nice, very chatty and despite some problems with the van, transfer wasn't too delayed. Transfer was on time leaving both directions, although they moved our time fowards leaving but only a little, there was enough space for our luggage and ski's.
Cham Express - used them last for transfers in September. No problems with them. Nice to be able to book online so didn't need cash for a driver (with Alpybus you pay the driver and need Euros to do so). Was out of season and landing my flight was delayed. Phoned to tell them I was running 15 minutes late and they waited for me quite happily.
I have also had some bad experiences with transfer companies over the years, the worst resulting in a very expensive taxi. At the time I was livid with the company involved and swore never to use them again and to darken their name wherever I could. However, time is a great healer, but also in hindsight the circumstances were beyond their control and were for the benefit of the majority of others travelling rather than me. It would appear that this is true for most of the people that have had negative experiences.
I would advise however to always have a back up plan (lots of other posts around trains and buses), avoid the last flight of the night into Geneva and never assume that your insurance company will pay for a taxi when you miss your transfer...