I have an account with smartname - at first customer service was a hassle. I was never able to get a reply from my rep - i wrote a post about it on my blog and the big guys at smartname read it and sent me an email about it.
Things have been better since then.
I really like the fact that you have 3 options of parking domains - a regular parking which makes the most $$, a store - if you have a specific item - and the 3rd option which is geared more towards complete SEO optimization.
I am making the most money using the 1st option, regular parking. You can also include your own google adsense ads, which obviously gives you 100% of the money when clicked.
Some of my parked domains also rank well in google. One site ranks third in google for a keyword that gets right around 1K monthly searches and my other parked domains are all indexed..
Overall they are a pretty decent parking company. I have made about $20 in 3 months with 2 domains. I dont think I'd make that much if i parked them at sedo. I also have about 15 domains that make about $1 a month.
You can also list your domains for sale
try it out - there is no concrete answer when it comes to parking.