What is the easiest way to obtain an invitation to the E-Rewards survey site? Also, I had trouble finding a detailed comparison of this site versus something like OpinionMiles? Is it really that much more "lucrative"?

I wasn't aware that it is by invite only, but I have luckily been a member for a long time.

I don't know how lucrative it is, but I can usually earn 2000 miles on various airlines every month. That is for $100 in e-rewards.

And that is doing every survey they invite me to complete. Usually 5-7 dollars per survey. Every now and then they give me a big one for like $75 bucks.

Yeah, I don't think you need an invitation anymore. For instance, you can join directly through the Hilton website: http://hhonors3.hilton.com/en/earn-use-points/more-ways-earn/index.html

Be aware that if you join through a hotel program like Hilton, you can only redeem your e-rewards dollars for that hotel program and not any other hotel program offered such as IHG or Club Carlson, but you can redeem for any airline. Similarly, if you join through an airline program, you can only redeem for miles on that airline, but you can redeem for all hotel programs.

as far as I am aware it is invitation only from a sponsor [ ie airline etc ]

I find it quick and easy to fill in these surveys and I usually end up with several thousand avios per year when I exchange

Appreciate all the information!

Note that people can end up getting slightly different e-Rewards redemption options for no reason why anyone can figure out. example- For a long time, some folks could redeem $100 for 7K Hhonors points while others got stuck with a worse rate , and us in the e-Rewards thread in SPAM (come over there for lots of program discussion) could never quite find a definite pattern. I've also got Iberia Avios for 3,000 per $100 and I think others only get 2K for the same $100.

e-Rewards oddity #2- even though IHG cut back on what counts as a status point for 2013, at least this year PC points through e-rewards still count toward gold/platinum status.

e-Rewards gives you the best bang for your buck at a least 100 miles or better per $5 survey, but if you've got more time than money you can rack up more miles per month at Opinion Miles Club.

Harris Rewards is even worse in terms of redemption rates- 800 points= 200 miles for Delta or US Air, so a 100 point survey from them is only 25 miles. (But since Delta pulled out of e-Rewards, I'll take my sky pesos where I can find them)

I did my first cashout from Peanut Labs via points.com over the weekend, and will report back when they let me know how many miles/points I can get per 100 'units'.

Southwest Rapid Rewards signup here.

American Airlines signup here.

I note from replies that obviously in the US you can enrol for e-rewards which is a bit different from the UK where it is invitation only

handy to know these things

Well, the pages mentioned above contain the invitations. They may be opened for anybody, or received personally. Also, they are usually valid for a limited time.