I've been meaning to get this review up for a long time now so here it is. Read on to see whether or not I think the upgrade is worth it.
Is it worth it to join Clixsense as a premium member for $10?
Here is my opinion. It has been 8 days now that I have been a premium member. At first, I thought it wasn't worth it because I wasn't getting many 20 cent, 10 cent, 5 cent or even 3 cent clix from clixsense. But then I realized that everytime I checked my clixsense account, provided that I waited at least a few hours or so, I found around 10-15 clix available again. About half or a little bit less are available to me as a result of being a premium member. I get around 10 or maybe more clix that say "the above ad is available only to premium members" below the ad. Check out the screenshot below:

How a Profit Can Be Made
10 ads to click on top of the original clix from being a free member takes about 5 minutes. If you can spare 5 minutes extra time at the clixsense website on top of whatever time you already spend clicking on the ads, you are clicking:
-10 ads a day (10 cents)
-70 ads a week (70 cents)
-3650 ads a year (3650 cents or $36.50 year)
You can see from above that you can make $36.50 - $10(cost of membership) = $26.50 of profit a year from clixsense if you make an upgrade.
No Guarantee
I can't guarantee that you will get as many premium ads as me but I know that I can only get at least 10 premium ads a day if I check around 2-3 times a day. The more often you check, the better chance you have to getting ads and making the membership worth it. I should also add that there were over 500 ads available for me to click instantly after I became a member so that is $5 worth of clix if you want to spend the time to click all of them. I took a little less than a week to click them all. I didn't include the $5 in the profit. I only included the profit you can get from the new daily premium ads that appear everyday. They disappear fast so you should click them as soon as possible. The original 500 that appear when you upgrade will probably last a long time so you don't have to click those as fast.
Here is the sign up for those that have not signed up yet to ClixSense:
ClixSense Sign Up
Staying as a Free Member
I would like to add that i think it is a great way to make some extra money even as a free member. At the time that I didn't upgrade yet, I still got many ads to click. Being a premium member means that you will need to set aside more time to click the ads but you can profit from the upgrade as long as you check your account frequently. I would say that I am happy as a premium member of ClixSense. I am almost at $20 now. Many thanks to FallenSage, who registered under me and upgraded. I made $5 from the upgrade since they have a policy where the referrer gets $5 for every upgrade. Here is a snippet from the My Account > Overview page:
"For the month of May 2007 you will be paid $5 for anyone who you refer to ClixSense.com who upgrades their account to a "Premium" member account."