Recently, we bought the Acer Revo to my Mom and Dad for a browsing machine. It's otherwise okay, but the internal WLAN antenna lets you wish for more.
Mom had reported Internet to be stucky, so I had a look. With the help of the InSSIDer program I found out reception to be around -70dB. But what was amazing was that plugging in her favorite USB stick (old, transparent, probably USB 1.1 era) made reception fall at least 5dB. Essentially, it makes the difference between 4 bars and 2 bars in the Windows internal gauge.
Telling now these old sticks must go. I bet many users around the globe never come to think their USB sticks might interfere with their WLAN. I checked them all, now. Out of our collection, 2 kinds drop the reception and one actually seems to raise(!) it somewhat. The USB port in question is not even close the WLAN antenna.
So, if you're considering an external antenna to your Revo, check your USB sticks first!