Wireframe? Mockup? Requirements? Whats best!?

I'm in the 'meat' of a project to redesign and re-architect a SAAS product.  For the project, we used really basic tools to complete wire-frames, workflows and requirements.  For wire-frames and workflows we used Microsoft PowerPoint and for requirements we used Microsoft Word.  I know there are better tools out there, so as the project was progressing I took to Google to see what other Product Managers were using.  Here's what I found:

Mockflow and Balsamiq are both great tools for wireframes and workflows.  I am sure many of you are familiar with these tools, but if not you can register for a free trial of either one.  The pricing models for both (under $100 per user for 12 months) are also very compelling for what they provide.

What I really like about Mockflow (which is what I ended up using) is

• Collaboration was extremely important to me.  My team is based in another location, so the ability to have both of us logged into the product at the same time to edit requirements was extremely helpful.
• Exporting different workflows so that the team could see the work I had completed was also very important.  In Mockflow, this can be exported in a variety of formats including PDF, Excel and PowerPoint. 
• Images can be uploaded to either product, which was helpful because we had a team design screens for us (PDF) but as the project evolved we needed to edit those screens.  Mockflow allowed me to important images quickly and then create mockups over those screens.
• Workflow is an extremely important component to the project.  I had several screens that needed to be designed, and Mockflow allowed me to insert screens AND link them to subsequent screens which helped the development teams understand the workflows

What could be improved on Mockflow (yes, I am a product manager so I have an opinion here)

• The Image up-loader could be improved.  I'd really like to drag-and-drop files, and instead have to upload and THEN drag and drop
• Grid sizing cannot be done - this is EXTREMELY frustrating.  I might be missing something, but from a UX perspective, it needs to be improved (I think Balsamiq does this better)
• Inability to export the workflow AND the wireframes in one document - it has to be two

Overall I'm happy with what I chose - but am wondering if I am missing something.  As a heavy Mac user, are there tools that are better for Macs?  What tools do you use?  What are the best?  What are the worst?