I wouldn't trust it.  What if that one in thirty happens on something that is a "one time" opportunity and you cannot redo it?  I wouldn't trust a card that gave me that "recording has been stopped" message or the buffer even one time.  The "one in thirty" wording you posted indicates you have had this happen more than once.

Transcend is probably the best of the "bargain brands" but I see just enough of what you report that tells me Transcend QC is not up to that of better brands.

B&H has some pretty fair prices now on SanDisk Extreme Class (10) media.

EVERYBODY LOOK HERE. if yor machine says recording stopped this is because of you aren't read instruction manual. when you use a different or new cad in your 550D you have to format it when its in machine. for doing this change your photo mood to manuel or other manuel mods. then clik menu button then clik format thn clik deep format and let your machine to start formating your memory card. you can find more instruction at 550D manuel book

i lived this problem too then i read this in instruction manuel. i tried and my problem solved

patriot lx series class 10.i know this problems about transcent but this problem hint is a general hint in book so i write there

EVERYBODY LOOK HERE. if yor machine says recording stopped this is because of you aren't read instruction manual. 

No.

It's because the media card cannot keep up with the camera.  A buffer bar appears on the LCD, fills up, and when full the camera stops the recording because the buffer can accept no more data.

Media cards generally come already formatted and when placed in the camera will pretty much function for the first run (unless the card can't keep up with the speed at which the camera is trying to write data).  Some of the best brands will continue to function for subsequent uses if not formatted as files are deleted or erased until they finally malfunction. 

"Bargain brand" media can malfunction or corrupt after just a few uses.  Formatting can correct this but in the case of media that is too slow for the camera in the first place this is no guarantee. 

All media do not necessarily function at the speed class rated.  A case in point:  Kingston Class (6) and Class (10) SDHC cards are documented to have had the buffer overrun and recording stopped problem after just a few seconds of recording in both Canon and Nikon video capable DSLRs.

We will see just how long it takes me to get my next error. I formatted the card today after backing everything up. I will come back and post here with my next issue. I am at image 3800 exactly (the last shot was 3799).

Went out to a baseball game tonight and the first time I tried to take video, I had the movie stop recording automatically. I didn't have a problem after that though. As I said, I would come back and post where I was at when it next happened and well, it went to 4196 before I had an issue. I ordered a Sandisk Class 10 card last week, so hopefully the days of errors are in the past.  I was able to record the next 120 videos without an issue aside from the camera getting pretty hot at one point, so I began to turn it off between innings and that seemed to do the trick just fine.