One of our favorite extensions is Wysiwyg Pro, which works great with Joomla 1.5.

TinyMCE, the default editor that comes with Joomla, is fine for editing if you're a geek and you know exactly what you're doing. But if you don't -- and that's most people out there who just want to get some simple editing done without a degree in IT -- TinyMCE is really hard to use. There are a number of big problems.

• There's no way to link to a page on your site within the editor by browsing. You have to know the exact URL for where you're linking, which means opening an alternate window and copy/paste the URL to the link window. (I've noticed that some users don't do so well with a pile of windows.)
• The image button works great if you know the URL of the image you want to link to. Again, no way to browse.
• The terminology throughout the TinyMCE interface is very geek oriented. It talks about URLs, ID's, classes, etc, rather than talking about a web address and orienting the image right or left.
• There is no simple way to copy from MS Word and paste to TinyMCE without either getting a page full of horrible MS "HTML" (I do use the term loosely) or else pasting to Notepad first, then copying/pasting to TinyMCE. That's one copy/paste too much for most users, and they're absolutely right on that point.
• TinyMCE has a nasty habit of putting in all kinds of extraneous code, but stripping out code you really want to keep.
• There's no straightforward way of linking to a document (think PDF, Powerpoint, or anything like that). You have to upload the PDF to the media manager, then remember the URL and enter it in the link dialog box.

When we moved to Joomla 1.5, our editor choices were very limited. Fortunately, the editors keep adapting, so there are more choices now than there were in February. But we have chosen Wysiwyg Pro for our clients, and we're very happy with our decision.

•  The link dialog box is totally awesome. You can link to another page on your site by browsing, an external site (preview of the page provided for you), or to a document -- and you can upload that document right when you need it, too.
• The image button has great alignment tools, either via float or by a given class for the image.  You can upload images right in the dialog box.
• The terminology is straightforward for the most part (though it could be improved, it's definitely better than TinyMCE.
• There's the awesome "paste from Word" button that allows a user to paste into a box first, then enter the content into their document. Hey, a actual direct control-V type paste would be better, but this is a great start and miles better than TinyMCE.
• The code WysiwygPro writes is actually halfway decent, surprisingly.

The only drawback for most is the $54/site license fee for the editor.  But consider what it saves us in tech support and training time for our clients! An intuitive editor is worth every penny. I encourage everyone to fold this editor into the cost of their web project and get it to your own clients.