The company I work for is 'using' AutoCAD Electrical. We are not using it to its full potential, but we are slowly making progress. We have not had problems with AutoCAD E. crashing any more frequently than AutoCAD regular did at my previous place of employment, If you do purchase Electrical, be sure to check the min. specs for the computer published by AutoDesk and meet them with room to spare.
I think that FOR WHAT WE DO, AutoCAD regular and some custom LISP routines would better serve our needs. But we don't have any LISP gurus, so thats kind of a non starter.
The drawings themselves will open with no problem from LT to Electrical. The file format is the same (except for the standard deviations from release to release.) Do not expect, however, that that is the end of the conversion process. You will need to change each of the symbols to AutoCAD Electrical COMPONENTS. Some of the components may exist, the rest you will have to build yourself. Until you get a base library built, this will be a tedious process.
AutoCAD Electrical is a full copy of AutoCAD, with some extra stuff added to handle the electrical side of things. Anything that you can do in Vanilla AutoCAD, you can do in Electrical.
I'm not sure what you mean by multiuser, you will need to pruchase a license for each person who will be running Electrical. To my knowledge, you can not have 2 users editing the same drawing, Electrical does however have a project manager which collects individual drawings into a single project. This allows you to have different users working on different pages of the same project - within reason. Don't expect to have real time updates as user 1 adds components to page 1 while user 2 works on page 2.
Modifications for As-Builts are always a pain, but no more so with Electrical.
The drawing that you posted looks more like what Electrical is designed for than what I'm doing. So I'd say that it should work for what you want to do. That said, BEFORE you drop the $$$ for the software, get a reseller to look at some of your existing drawings. Have them tell you what will and won't work. Develope (or use the one that you already have) a relationship with that reseller and make them work for the sale. You WILL need a class for your users. In fact you will probably need a couple different classes over the first 6 months of use.
Initially, you will want to go to a class on the basics, using project manager, adding components and so forth. Pay particualr attention to creating custom components. (You will be doing a lot of this.) Make the teacher go through this aspect while you create components for your application. Creating components for the excersizes in the book is all well and good, but not what you will be doing on a daily basis. Your existing blocks can be converted to components - but the process is far from automagical (like you will be led to believe).
After you have used the software for some time, you will probably want a second class with a less formal lesson plan - more geared towards answering specific questions about process in Electrical and how things are done.
Good luck with whatever you decide.