WalMart, Target, Radio Shack, Best Buy,and Staples, all have the Sandisk class 4 16GB uSD card for right around $19.99.
I was looking for a cheaper uSD card but this is what I found in all these locations for a 16GB uSD card.
I'm a got to have it right now kind of person, so I purchased it. Got it home, next day I wound up deciding to format it to FAT32 so Link2SD would work. Loaded 20 apps on it before remembering to do the Speed Test.
Ran the speed test and was flabbergasted by the 38MB/s that I saw for the read speed. Ran it again and I got 40MB/s. Ran it one more time and got 39MB/s
I thought I would get right around 28MB/s near empty with the better quality uSD card. I was not expecting 39MB/s Wow!
I have since managed to download fresh apk's of the apps I had originally, and moved and linked all to the uSD card, except widget apps and those that required an active internet connection.
I have moved all other files I originally had on the uSD card back and all told have a little less than 6.5GB on the biggest partition. I still get right around 28MB/s read speed.
This just goes to show that the class of the uSD card doesn't mean anything when it comes to read speed. I was getting 38MB/s with a near empty class 4 uSD card. Quality seems to have a lot to do with it.
Note: SD speed booster aps didn't seem to have any noticeable affect for some reason. In all these tests I consistently got around 5.0 on the write speed, plus, with Link2SD installed and over 150 downloaded apps to the uSD card I was getting amazing boot up times (time from home screen on to being able to actually use an app was less than a minute)