We joined up with ESP in 2011 after trying two other big name multi channel solutions and much research.
This is the best solution for us, we sell across multiple platforms and have also got a web site solution all designed and hosted by ESP.
Initial set up took a little time, but the support and training was superb with help at all points of the setup to it going live. We had a few teething issues which were resolved quickly.
The system runs very smoothly and fast enough 99% of the time with the odd issue every now and again. These issues are always dealt with quickly. All systems have the odd issue which is no surprise due to the complexity of all the data being dealt with.
Ongoing support is good, we have a very good account manager who looks after us, makes suggestions of improvements and informs us of up and coming changes etc. Training sessions are always available for a refresh if required or if we have a new member of staff that requires training.
The pricing structure in my eyes also makes perfect sense. ESP take a small percentage of the sales we make, meaning that the more they can help us sell, the more they will get. It's in their interest to help us sell! So we both win. Companies that offer free or low costs solutions normally means the support is rubbish as they can't afford to employ enough staff. ESP does the job of 3 people so is a small price to pay in comparison.
In conclusion, ESP is not perfect (hence 4 stars) but is about the best solution available in my opinion! I would recommend to anybody (well maybe not to our competition!)