I have been with them for many months now and I honestly cannot find much to be critical about. The information I provided for the initial account set up was handled professionally and without any issues.
There were two billing issues I had that needed some intervention by CDG Commerce, they got right involved and the issues were cleared up right away. These issues were related to a client's needs and had nothing to do with the CDG services.
I opted for the CDG gateway (as opposed to Authorize.net) and it is a very basic, easy to use system that allows integration with my other systems. I didn't want a Payment acceptance solution that "did windows and toilets", I wanted one that accepted Credit Cards online. That is exactly what I got, no surprises.
I've had a 2Co account for a bit over a year now. They have their share of problems but they never affected my business to the point I needed to change 3rd part processors. During their DDOS spell many months ago I did start looking around and that was what led to our decision to obtain the CDG account.
For just getting started 2CO is ok, their forums are a place to stay away from as I think their Reps there do not display a very professional attitude. If I had to do it all over again, I would have just went with CDG Commerce. Covering a small fee for a few months when you get started is much better than having to change billing over to another processor. It is this reason that I still have a handful of clients that use 2CO. I just kept that account active and have a handful of clients that get billed through there to this day.
I think I can count on one hand how many PayPal clients we have. For our target market they are not a big player for us. I have had zero problems with them though.
When I had the DDOS issues with 2CO I applied to PaySystems before I applied to CDG Commerce. PaySystems is the poster child of the poorly run processing companies out there. During Pre-Sales they were quick to answer, the problems really started when I faxed the Library of Congress over to them for Account Acceptance. They lost all my confidential information! Not only that but the sales rep that I had actually wanted me to fax everything over again. Now I know that the fax transmission was successful, their Underwriting Dept just flat out lost the information (by their own admission). I think it was like a month later that the sales rep called me to find out where my account information was (for the second time). I guess he must have missed the 4 voice mail messages and various emails I sent him.
After I discarded them as a viable option I began to hear all kinds of horror stories about them here. From anonymous client account cancellation, to much more serious issues. A detailed search here will bring many alarming problems to light I'm sure...
These have been my experiences, your mileage may vary...