I have just started using 2CheckOut inside the last 2 months. I thought they were good looking and decided to try, afterall, if it goes wrong you can always move to a different processor. Here's what I have noticed:
1. If you have even a small number of orders it will literally take several minutes on a dial-up modem to view them. Their system is slow as mollasces.
2. Confusing to begin with, but after a while it gets easy to use.
3. No problem getting money into your account. Although I did notice a slight discrepancy after they wired me the money.
4. Slow response rate to customer enquiries. Any response you do get is mostly a copy-and-paste script.
5. Generally slower for customers to add products to their cart when compared to the likes of paypal.
6. Seem to have some trouble with their servers going down and miss-timing subscription payments.
All in all they are ok. But if you expect many orders you will need to expect long delays in pages loading, so it will take longer to process orders etc etc.