I went into a Telecom store today with my HP Pavilian DV7 Laptop, and installed and speedtested both the Telecom MF636 & Sierra Wireless 885U before purchasing.  The reason why i had to bring my laptop in to test for myself is that the staff in the "store" had no idea about the products the day before.

The staff member tried to tell me (or sell me) that the Sierra Wireless 885U have better reception!!!! that's why it's double the price. 

Here are my speedtest results at 3.30pm this afternoon inside their store on my laptop:

Sierra Wireless 885U

Download: 2.74mb/s
Upload: 0.11mb/s  (yes, 0.11!!!)

Telecom MF636

Download: 2.90mb/s
Upload: 1.25mb/s

So, needless to say, i purchased the Telecom MF636.

As a word of advice take your laptop into your local retailer and test it yourself before purchase!!!!!!  You might just save yourself some money.