As I mentioned before, the 0.6mm nozzle is working well for me as long as I limit the speed in Repetier to about 80 mm/s for all types of movement.  I am quite satisfied with the results.  I am not going to switch to a .5mm nozzle because it is working fine and I am still pushing a high volume of plastic.  Also, there is some advantage to the fact that the carriage doesn't move as fast.  Namely, less wear and tear on motors, bearings, etc., motor drivers stay cooler, quieter operation, less problems due to acceleration.  I guess I shouldn't have called it "useless", but I was just frustrated with the fact that I hit a limitation that was unexpected.

If you are getting blobs in your prints take a look at your retraction speed and distance.

It's not the kind of blobs related to retraction (look at the pic I posted above).  It can't extrude smoothly over a certain volume limit, even during a straight section.  I'm not talking about a decrease in quality.  This is an inability to print anything.

It is true that I am extruding a "crapload" more plastic than with a smaller nozzle, and I am quite happy that I am able to print faster.  No complaints there.  But my main point is that there is really no benefit to using a 0.6 mm nozzle over a 0.5 mm nozzle if you just have to run slower.  I would rather have the ability to get better detail when I want it while still being able to push the maximum volume of plastic when I want that.  In hindsight, I would have ordered a 0.5mm nozzle to get the best balance of both worlds.  Hopefully someone else who is dreaming of super fast printing by using a bigger nozzle can learn from my experience (that is assuming I am not doing something else horribly wrong).

Because its impossible to make a statement of 'I print at X-speedmm/s'.. as the 'print speed' changes depending on if its Interior perimeter, exterior perimeter, infill, top/bottom, first layer, bridge..

It also depends on tool-path length for that travel. At each transition of direction it will slow down to the 'x-y jerk' value (with caveats, too many to list here). It will then ramp back up to its relevant tool-path speed using the acceleration vectors in EEPROM.. It also depends on Direction - a movement in the Y direction alone will move faster than a Diagonal movement in the X/Y direction.. This is why often 0° offset rectilinear infill can be 4-5 times faster than hexagonal or even 45° offset rectilinear....

So in short - there really is no such thing as 'I print at X speed' - and if you actually average it all out its usually much slower than the numbers would infer due to complexity of movement screwing it all up. 

Now - regarding printing with a .6mm nozzle in general - You are moving a crapload (I believe thats the scientific term ) more volume of plastic than a .2/.3/.4mm .. Elmoret or someone smarter than me can give you the math I'm sure. You can't just expect to move a substantially increased volume of plastic at a faster physical speed - but instead you move more plastic for the same given speed which means you need to overall extrude less.  So you don't run it 'faster' in terms of linear speed - as you are already moving *more* plastic which is where the idea that you can print 'faster' with a .6mm nozzle comes from. Your axis dont move faster, but for each movement, you do move more plastic, requiring less *total* time... by exploiting techniques of printing 1x60mm perimeter which is faster than printing 2 x 40mm perimeters..etc etc

Then theres the whole other thing regarding the different back-pressure and its impact to flow-rate/speeds as a result in the change of nozzle size with a constant melt-zone... but that's beyond my ability to articulate.

To ensure quality prints on a Stock solidoodle (meaning the mechanics, not the hot end so much) you really shouldn't run the exterior perimeters over 55 - you can push it based on the particular shapes geometry but it's a loosing game above that. Internal perimeters, happily will go up to 80+ (even 100) without turning too ugly... Infill is usually best served at the same speed as interior. Bridges boil down to a magical combination of temperature and filament.. There is values that 'usually work' but the 'Best' speed/temp combo is fairly dynamic depending on filament etc.. And none of this needs to/should change based on Nozzle size beyond some minor tweakage knowing the cause-and-effect of that setting you tweak.

tl;dr - Theres no such thing as 'I print at X-speed' , and, you print 'faster' with bigger nozzles by virtue of moving more plastic, not physically increasing speed.

Unless you have something else strange going on?

It will outline, with fairly explanatory pictures, the Maths Slic3r uses for flow rates

perhaps you need to switch to 3mm filament... this is the only case i know where a 3mm filament is better than a 1.75mm..

Is there any case where 3mm filament is better? more moire, and more resistance per cc of plastic squished out.  The resistance going from Xmm filament to Xmm nozzle diameter is not linear, it's some exponent, so it's easy to put through the 4 times more needed 1.75mm than 3mm filament.

The only case I see for 3mm filament is if you can get it cheaper, if it absorbs less water (smaller surface area to volume ratio), or if your thinner filament has relatively more diameter variance.