Don't thank me. You could still have a hard time understanding this, you'll see 
Inside maya, nurbs curves are represented with parametric equations. These are functions in form x( u ), y( u ), z( u ). Coordineates of each curve point are calculated this way. Argument u is called a parameter. Each single value of u represents one position on the curve.
Now for any curve we can tweak the equations so the parameter u falls inside the desired range. If the parameter range is say [ 0.23, 5.43 ] then u=.23 represents the begining of the curve and u=5.43 the end.
For single curve it is pretty irelevant, but it comes to importance when couple of curves need to work together - i.e when we build the surface.
For example, when doing loft, maya needs all curves to have equal parameter range. Otherwise it might screw up the resulting surface.
Don't mix this with number of spans. It is different thing. For best results when making surfaces, both; the span number and parameter range of the curves should match.
If you have a curve with 0-1 parameter range and cut it at parameter position u=.25 you'll end up wit two curves having ranges [ 0, 0.25 ] and [ 0.25, 1 ]. Its easy to forget about this and watch as your lofts or boundaries come out totally mangled, asking yourself what the hell is wrong with this nurbs stuff?
This is why you should always rebuild to 0-1 range - that way each curve can be combined with each other safely ( of course watch for number of spans also )
Rebuild surfaces/curves is operation you'll do pretty often and it's very important to understand what it does and what all these options actually mean.
There is pretty good general info on curves inside maya's docs. Read it once in a while.
Also, I think there is basic curve stuff video tutorial on alias site.
Blend tries to keep tangential continuity while connect mantains only positional continuity but inserts spans with multiple knots ( which is what you don't want in some cases. It's kinda 'dirty' ).
Prior to attaching with blend, add more spans around connection on both surfaces if you want to keep the shape.
I've tweaked the CVs a bit to gain larger radius for the rear fillet ( compare the isoparams with previous one ). Circular fillet needs nice and easy curvature. In order for circular fillet to work your smallest surface curvature radius should be bigger than desired circular fillet radius.
