Grisoft AVG slows systems?

I've noticed on two different PC's with different operating systems (ME, XP) this program *seems* to slow things down quite alot. Do others find this or is it just my allergic reaction to anti-virus software?

Anti virus software is a huge drain on the CPU. And in only promises to get worse as more fools develop more viruses that such software has to check for. Running current A/V software on older CPUs can result in significant performance loss.