I have used the CSS pair in the past, but at Cisco Live I spoke to the ACE team in the World of Solutions and ACE pricing was quite similar to CSS (say the ACE 4710 1U model) and it looked to be an effective solution. ACE is also soon available on a Network Module (ACE30 - could be out now) and that looked great.
Be aware of the similar restrictions that apply to CSS if you have the pair geographically separated. With ACE, you would need a GSS above.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.