Pretty decent parking provider. SEO... you can customize a punch of stuff on the page like description/meta tags/add some content which definitely helps.
You should test different parking providers. Parked may be the best for some of your domains but not all of your domains.
It really depends on the niche. I've done some major testing at different parking providers and pretty much have a formula down for what gets parked where. Lately, I've been "re-experimenting" and moving domains around trying to see if I'm missing out on any extra revenue. There really is no "best" parking provider. Overall, I disapprove of Sedo... yet they are still decent for certain domain niches. If you need some more help, feel free to PM me the niche and I'll give you my opinion on what might work the best. Like suggested, you might have to move your domain around till you find the right one. Domain Sponsor has currently EXTREMELY surprised me in terms of revenue w/ CPC/CPM.
WhyPark is certainly the most in-depth when it comes to variety and detail of what they provide in terms of page templates and adds. The only catch is you pay $100 for 100 domains. Its a lifetime membership fee however, which justifies it.