Prof X's Origin and Introduction of Juggernaut Can't Compensate for Poor Art and Story
This issue of the X-Men is notable for a couple of reasons - first, it contains the origin of Professor X; second, it contains the origin and first appearance of The Juggernaut.
But the execution of this issue is very poor. First of all, Jack Kirby's attentions were probably elsewhere during the creation of this issue. He just provides layouts which Alex Toth finished and Vince Coletta inked. But Kirby's layouts must have been very preliminary indeed, and Toth doesn't really build much on them, resulting in many very static posed characters - even during battle - made worse by the fact that most of this issue is the X-Men listening to Xavier tell a story about his past, with very little actual fighting until the end.
That brings up the second really big problem here - the plot. Cerebro wails, off the charts, and Professor X knows that means his old nemesis is attacking. Trouble is this contradicts Cerebro's functions - it's supposed to detect mutants, and from the story we are told in this issue, The Juggernaut is not a mutant! Then, the X-Men spring to action, building a thick ice wall around the mansion, a covered trench, two electrical barriers, and a series of gas grenade mortar ranks - all in exactly 5 minutes! And yet, they forget to use the mansion's already existing steel barricades until near the end of the issue when it's almost too late!
If that weren't bad enough - rather than try to stop The Juggernaut, they sit around Xavier's study whilst he relates his past history of pain and woe for the whole issue, while Juggernaut breaks through defense after defense.
There's also a bunch of mild annoyances here too - Iceman starts using gravity-defying ice slides with no means of support, and there's some general buffoonery with Iceman, Angel and Beast all spring into battle and running into each other like the 3 Stooges.
Even the backstory of Xavier and Juggernaut, to which so much time is devoted rings as false, with all the characters (particularly Cain Marko) acting in such stereotypical ways.
Although I'm glad this issue happened, I can't really say it's a particularly 'good' issue.