Ok, we had to spend each morning (including today) troubleshooting the 503 errors that were caused by this. We completely uninstalled twice now (no idea why it wasn't gone after first try), hoping it will not come back and it will not break our store again tomorrow.

Your lack in communication did not help, we're getting a refund.

i'm woundering, that so many people buy's these very buggy and with a half hearth developed extension.

I must say, i was silly too, hand have buyed them vor any time too, but i'll never use them again, while it gives most better combinations to speed up magento without generating static pages on the disk from dynamic before.

Example for unix users:
Switch the Apache to an other port as 80 (ex.: 8080) and place the varnish cache proxy before the apache. When every one use SSL certificates, switch the varnish listen port to 6081 and place NGinx as proxy for the Varnish with port 80 & 443 to handle SSL requests. Optional use a S3 Cloud (ex. Amazon S3) for the /skin & /media directorys. The S3 is not a must have, but reduce the pageload time ~35% additional, while your own server don't must deliver all pictures himself

Then you can see magento fly without any troubles. In my case the pages from my magento multistore loads under 75 - 97ms worldwide. I've reports from customers in Australia, Asia, europe and north & south america, they report me the loadtime. What i want more for free?

The best: You don't must edit core hacks or extension to your magento installation ...

interesting. can you show me your url?
dykwia at gmail.com

i can give you a short description from me, how i made these combination within 20 minutes, but i don't post my store urls in magento relevance bulltein boards about hte reason, that i become many messages from anyone, how want to know, how i make it. my buisness is not magento.

At the moment i write in the evenings an tutorial and when i was ready with them, i post them in the official magento bulletin board, not in these. I hope for understanding ...

Sure thing. If you can let me know when you posted it and where, that's awesome.
Already asked my host about possibilities.

Yes, webserver cache can be far more efficient and less susceptible to differences server settings. Unfortunately, not all hosts server allows to using it. In this case needs to use pure software application based on PHP such as MTurbo.