The Bendis Board goes for the nostalgia vote:
“I was an impressionable 9-year old in 1996, the year when Xaiver and Magneto’s respective consciousnesses combined to form Onslaught. I read some of the crossover (mostly just the X-Men and Excalibur issues) and enjoyed it, but my tastes had not matured or were not fine-tuned by age or wisdom. I see it’s collected in a few TPBs and I’m interested in hearing any thoughts on the crossover by those who read it. I think I may take the dive if I hear good things.”
“I read the first trade of the original Onslaught collection, and to be honest, it wasn’t as horrible as I imagined.”
“I enjoyed the core titles involved immensely when I read them first, and still enjoy re-reading them every so often. I didn’t read too many of the minor crossovers but the few I did were done reasonably well. I loved the fact that even though it was mainly a big x-event, it crossed over with the MU too. And I REALLY loved that they relegated their main x-character to the background for almost the entire thing (having Wolverine helping the emergency services because his abilities were almost no use against Onslaught).”
“I passionately love the Onslaught saga. Blatant marketing gimmick that was meant to make people buy every single Marvel comic? Yes. Will I ever invest in a similar endeavor the way I invested in that one? No. But I think it’s probly one of the best, most under-appreciated Marvel stories to ever come out.”
Dammit, now I have a strange desire to read the damn thing.