I have recently had a client who already has a Drupal/Ubercart powered e-commerce website. The client though had an issue, the current payment processor only had an offsite processing for credit cards which meant that the client was using some percentage of potential customers because of an extra step in the checkout process.
We started looking for a new payment processor, and there are a few options we were looking at, Virtual Merchant was one of them. So we started looking if they are compatible with Ubercart. And to my surprise there was even no mention of either Drupal or Ubercart in the list of supported shopping carts.
So if you are (like we were not so long ago) looking if Virtual Merchant is compatible with Ubercart, serach no longer, you have found the answer, YES THEY ARE.
If you need help with integration Virtual Merchant or any other payment processor into a Drupal / Ubercart website, we certainly could help you.
P.S. here is the link to the Virtual Merchant Drupal module https://drupal.org/project/virtualmerchant