We made this change three weeks ago and there is one BIG gotcha: before applying the Professional license, go to Priority Matrix and check the box "Allow requesters and technicians to override the Priority Matrix". If this option is not enabled, you will not be able to change settings of the Priority field on templates.
When we were considering changing from Enterprise to Professional, we looked for information on feature differences and found this marketing web page:
http://www.manageengine.com/products/service-desk/sdp-editions.html?index
This web page lists ServiceDesk Plus software features and shows which features are included in each edition. We specifically noted that the following features are included in the Professional Edition: Help Desk, SLA Management, and Incident Management. Based on this information, we assumed that all of the functionality related to Help Desk configuration and incidents that we were previously using in the Enterprise Edition would continue to be available. We had no reason to believe we needed to investigate further or change configuration of items such as the Priority Matrix.
Immediately after installing the Professional Edition license we realized there was a problem with requests created from templates not having priorities and due dates. Upon further investigation, I found we had lost access to the Impact and Urgency configuration and the Priority Matrix menu was missing. We could not change requester access to some fields on our existing templates because we could not disable the Priority Matrix function. We submitted a support request, which was not handled to our satisfaction. We finally got help from a Pre-Sales Engineer who arranged for a temporary Enterprise license so we could briefly regain access to the Priority Matrix menu area.
From a product standpoint, I don’t understand why the Impact and Urgency functions are not included in the Professional Edition. I feel they are an integral part of SLA management and it makes no sense to provide a Help Desk utility with everything else except this. I wouldn’t be surprised to find that the development costs to exclude these features are actually greater than if they were included. Based on the inconsistencies in the interface (Priority Matrix menu hidden, Impact and Urgency menu buttons visible but non-functional) it seems that the implementation is not entirely successful, which reflects poorly on the product as a whole.
I feel that executive decision-makers should seriously reconsider the exclusion of these features in at least the Professional Edition, if not the Standard Edition as well. If they continue to be excluded, then at the very least, the misleading marketing web page referenced above should be clarified as soon as possible. In addition, customers need a detailed checklist showing what items must be reconfigured before converting from Enterprise to Professional edition.