Coming from an almost purely Microsoft Visual Studios background, being a devoted user of UltraEdit and being new to SlickEdit, here is what little I can offer to the conversation.
I do mostly c#, perl, ruby/rails, t-sql, kixtart and other batch programming and have been able to do all of it nicely in UltraEdit.
If you want a lot of flexibility in being able to edit many different kinds of files, with code folding, projects/workspaces, for little cost, I would highly recommend UltraEdit and if you get it bundled with UltraCompare you have most of what you want (I think) and have saved money over SlickEdit.
However,
Even with their recently introduced JavaScript support, UltraEdit will never compete in the flexibility and customizability of SlickEdit, but that comes at a price both in dollars and the time it will take to learn all that Slick offers and how to take advantage of it, because the feature set is so broad and deep, that is a lot more learning than you will have to do with UltraEdit. I am still getting my feet wet and want to make SlickEdit my primary editor for non-Microsoft stuff. When they get their ruby act together more I will not be tempted as much to even look at another editor for anything else.
I hope this helps, I can tell you that either way, you will be getting a great tool.
Eddie