It can go some way to addressing the "problem" of the Corbyn surge. This isn't a problem in terms of numbers, or that plenty of MPs are worried they may face deselection (IMO, reselection should be a matter of course), but one of harnessing the new found enthusiasm and integrating the masses of new members into the party. Both could prove difficult because a lot of the new intake appear to either be very raw, or are so-called 'values voters' turned active. i.e. Political commitment is an expression of individual values and personality traits, hence Labour has "come to them" rather than the other way round. That in mind, the trusty old structures of the party might not be the best way of retaining and training these new comrades.
From what I can tell, Corbynmania possessed the properties of a craze rather than a social movement. That's not a value judgement but rather an appreciation of the type of collective behaviour it initially manifested as. Allow me to explain. Huge numbers of people were responding as individuals (heavily mediated by social media) to Jeremy's campaign. This is qualitatively different from, say, the hard work Anna Turley and the local party are putting in in Redcar yielding thousands of new recruits galvanised by the SSI closure, the government's refusal to do anything, and the campaign against. The latter is, forgive the ghastly phrase, 'immediately immediate' while the former has a certain dislocated character that appeared immediate thanks to the collapse in distance social media, and Twitter in particular, can simulate. As I've written before in a totally different context, that doesn't mean the feeling and commitment it inspires is inauthentic or hollow, but it does pose difficulties when translating that into real world action. Let's be frank, monthly CLP and ward branch meetings are hardly the best showcase for the party. You turn up wanting to change the world and debate policies, and instead all you get is hairsplitting about last month's minutes and points of order.
Momentum, which presents as an open movement working to "organise in every town, city and village ... to encourage mass mobilisation for a more democratic, equal and decent society" appears well suited to capturing and steering the tens of thousands of new members. It can sort meetings and arrange campaign activity without the (IMO necessary) tedium properly constituted meetings of the party sometimes entails. It can sidestep the logjams of party cliques ensconced in local apparatuses, or the recalcitrance of MPs and their offices to campaign regularly and/or take a lead in organising voter registration, or campaign officers who can't be arsed. And most importantly it can organise on cross-constituency bases by intervening in or starting community/workplace campaigns outside of the electorally focused work of the party's established Local Campaign Forums. In short, it presents as a free flowing, fluidic organisation of networks of activists that are characteristic of mobilisations in the internet age. Corbynmania started as a craze but went on to become something else. And as sociologists of collective action will tell you, it's what toppled Arab dictators too.
Understandably, not everyone is cock-a-hoop about Momentum. The proposal to "make Labour a more democratic party, with the policies and collective will to implement them in government" have led some to attack it for factionalising (a crime the Labour right are definitely not guilty of what with their networks of cliques, think tanks, and open factions). Apart from the hysteria, there are signs sober thinking is starting to prevail. Richard Angell of Progress has dispensed some friendly(ish) advice, and Labour First have finally come out semi-openly. If the Labour right want to claw back lost ground, the way isn't the fixes and dirty tricks of old - as outlined in John Golding's compulsive The Hammer of the Left - not least because they're open to easy exposure, but by the good old method of out-campaigning, out-recruiting, and out-arguing. The right have got to get persuasive otherwise it will never win the hearts and minds it needs to.
Nevertheless, all party members should welcome Momentum, and even sell-out husks like me should get involved where possible. I want to see a strong Labour Party and string labour movement. That can be helped by Momentum serving as a bridge that integrates new members slowly into the party, habituates them to working with others who they may otherwise disagree with while fulfilling immediate campaign objectives. And who knows? The new arrivals might teach the old guard a trick or two as well.