I just got into building rods this winter so I admittedly don't have a huge amount of experience to draw from. I started with a cheap CRB kit to get the basics down. Since then I've built 3 other spinning rods on MHX blanks. One on the mag taper series MB842, another on the spinjig series SJ843, and the last on a high modulus popping blank HM-P843. I am not unhappy with any I've built on, and all have seen their share of use.
So far my favorite build is on the SJ843 blank. It makes a good all around blank for what I do (chasing sandies, hybrid/striper). I paired it with an Okuma Ceymar 2500, used the 16mm Fuji VSS reel seat w/hidden thread hood (both shortened about 1") and split eva grip with PacBay Minima 4 guides (concept layout), and while I haven't weighed the setup, it is the lightest 7' spinning rig I have (too many to admit to owning).
I have no complaints about any of them built on MHX blanks so far, and I doubt I'll ever buy another assembled rod. I am hooked, pun intended. I've seen where some more experienced builders refer to the MHX blanks as second tier blanks, and I am in no position argue with that. But the ones I have built have exceeded expectations so far. Next on my list is a pair of baitcast rigs, but Ihaven't settled on the blanks I'll use for those yet. Seriously looking at the MHX Magtaper blanks for those too.
If you're not living on the edge, you're taking up too much space!