It is quite fun; I didn't even really notice most of the flaws people love to point out while reading it - it was easy on the eye and flowed just fine. I don't find unrealistic anatomy to be such a problem (how often do you see Mignola or Kieth taken to task for that?), it's mostly that he isn't consistent within his own style.
That said, the first Liefeld comic I read was when I got back from my "break" from US comics just after the start of Heroes Reborn - and that was just dreadful, coloured my opinion of him for a long time.
People will moan about Liefield but what they forget was how horrible New Mutants was before he arrived.
The last issues of the Blevins/Simonson run are dire. Truly. Blevins style never really did it for me, and though I'm starting to see something in the earlier issues the later ones (Inferno onwards) still look awful to my eye. You can find his art in the Mutant Massacre(he draws some of X-Men 211 trying to ape JRjr and you can tell which panels) Fall of the Mutants and Inferno. Oddly the rest of his run with Louise S is the only New Mutants issues which haven't been collected.
Liefield injected energy and dynamism into the title and made it something really worth reading again. Breath of fresh air.
In the 80s X-Men, New Mutants and X-Factor were top of the pile for Marvel and for a long while each title really deserved better art teams than they had. It's only with the arrival of Lee, then Liefield and finally Portacio that they look good again. Go read Xtinction Agenda and compare the issues drawn by Lee and Liefield (though he's not at his best here) with the other artists. Chalk and Cheese.
IIRC the end of Simonson/Blevins run is an overlong story set in Asgard basically leaching off the NM Special Edition/X-Men annual 9. I'll look up how long it was but it was running when I quit the title and they were just returning from there when Liefields run started