XYplorer Beta Club

is there any consensus as to which anti-virus program slows down things the least?

I think you just need to exclude XY from the scans. You should be able to do this with any AV.

For a good couple of years I ran Norton-something/2004 plus AVAST with satisfactory cost/benefits (but knowing that, despite clearly seeing that one was covering other's faults, I wasn't completely safe).
Last week I saw a small shop running the same pair on a pretty low-end machine.
Currently (since 2007, I guess) I test EVERYTHING suspect (not much, setups and .pps) at the virustotal.com website - and confirm that I wasn't secure even if I was able to install and run 43 different a/v solutions at the same time.
E-Set Nod32, AVIRA and AVG are the heavier solutions I've ever seen.
Some (specially the free versions) a/v won't allow .exe/folder exclusion.
I do not have a/v in 3 out of 4 machines - and only got 1 virus attack in 10 years, due to an accident occurred after a full year relying on internet cafés to get some decent connection and get some work done.

Joso wrote:is there any consensus as to which anti-virus program slows down things the least?

I can only offer my personal experience, which is that both Norton Internet Security 2010 and 2011 as well as Kaspersky Internet Security 2011 don't give me performance problems with XYplorer. There's one caveat regarding Kaspersky: on *initial* run of both the installer package as well as XYplorer itself, it can take up to 30 seconds before Kaspersky is satisfied they aren't malware. Subsequent runs aren't hampered, but with almost daily betas to install this gets somewhat noticeable.