Form-z
Maya
SketchUp

form-z not so intuitive but accurate.

i model in form-z but render in cinema 4d. the latter works on both platforms and is more or less a clone of 3d studio.

Have you considered Sketch-Up? It's a fairly new program that still has a few glitches but is extremely user friendly. I learned how to use it in about 3 weeks, plus there is a traveling classroom with lessons available at somewhat of a high price. There are also online tutorials which walk you through each tool and it's possible applications for FREE! You can download a free version...I think it lasts for only about 100 hours, but I could be wrong about that. Go to www.sketchup.com, you'll find all pertinent info there. Good luck fellow Aplle.

Both of these have a lot of promise:
Modo
Hexagon

Sketchup is fine as 3D "training wheels", and it is certainly easy to learn, but you will quickly bump up against the limits of what it can do. Sweeps and Booloeans are there, but very primitive, and its import/export options are a very limited.

Its a great place to start, but you may want to look at a more serious tool.

Wow, thanks adso. hexagon looks great.

I like cinema 4D quite a bit but mostly for it's quick rendering, not it's modeling.

FormZ 5.0 looks good. it finally has the ability to script. In my opinion it is fairly intuitive. Well suited to most architecture offices as Maya is a bit of overkill while not so accurate.

Vectorworks seems to be the drafting app for the mac. I used to use something called powercadd but i hope they are out of business by now.

You might also look into Maxwell, an up-and-coming renderer with some amazing abilities and features. First, it is accurate and extremely realistic. Second, when you buy it you are given access to ever version they make. That is, you don't have to decided if you want to use it on mac or pc or linux. You can use it from within maya or cinema4D, or FormZ (or rhino, max, etc on a pc). Currently it's not so fast but that should change soon.

Modo is nice, but still lacks the accuracy that Form Z provides.

In nurbs-driven programs such as Cin4d and Maya seem to have really shotty snapping options.

A lot more offices are utilizing the 3d abilities of their drafting apps - VW 11.5 and Archicad have decent modelers [if you are doing cartesian models]

Cin 4d has a decent Nurbs engine and makes motion animation very easy - control clicking keyframes, ect. Now that Final Render Stage 2 is available for Cin 4d - i'll probably use it more.

Form Z 6 has motion, but still a really rudimentary scanline renderer. [Radiozity is terrible.]

and of course Maya - which is great - but if you dont have someone there helping you and / or showing you tips, you can get lost.

Yeah Maxwell renderer seems pretty nice - but I'd like to see it beat mental ray.

Thanks for all the help, I'll stand by as more posts come in....
(What bugs me about Vectorworks is the difficult navigation around working planes that is more intuitive in a pure modeling program)

Forgot to mention solidthinking. It is basically Rhino, works on a mac, and is fully parametric. In other words, much better than rhino. Plus, it's pretty cheap compared to maya, formZ, or cinema4D.

if you're in school you can get form z for about $180 with a one year license, from www.studica.com They may have some of these other modeling programs talked about above, not sure, check it out.

I've been a formZ user for awhile now and I have to say that my frustration with the program has increased lately. The 5.0 release (and it's updates) are still pretty unstable on OSX, not to mention that the interface hasn't been revamped in ages, so the program takes up a lot of screen real estate and I find myself constantly wrangling with the work window and the palettes. It still feel like an OS 9 app.

I have been using "carrara" for 2 years for both rendering and modelling purposes...Its really great tool and easier than the others. If you have dopest system like powerbook or something bigger than ibook series you can render vray quality images..

carrara