A lot of Enterprise Resource Planning (ERP) systems in place today were installed in the 90's as part of the consolidation of point solutions or to deal with Y2K. At the time, a lot of effort generally went into selecting the most appropriate supplier and system, and significant money and manpower was invested in implementation …
Clouds and SAAS
It's a mature market - almost everyone has dashboards, document management, CRM wired into their ERP offering now. I see companies running it on a hosted service basis more and more, and that will presumably translate into cloud offerings once the web can offer the same interface richness and reporting facilities that you get on the desktop.
Putting business processes into code ever again is a sure recipe for a failure
I would say implementating an ERP system the "normal way", with business processes defined in the code alongside many low level and unrelated functions are just sure way to get into another trouble. Only this time, as things have sped up in the business in general, this trouble is going to surface sooner rather than later.
So what to do?
I would suggest taking only financial modules from the original package as bookeeping and other finance functions do not eveolve fast. The rest, and especially all market-related processes (as CRM and even production and other processes that are definitive for the chosen business model) are ever changing so process engines seem the only good bet in the long term. How processes defined in those engines are presented to users is another question (some kind of portal, probably). The real issue is this: making process definitions modifiable on a daily basis and without the need to ask a vendor to do it.
Organisation gets in the managers way.
I've always found ERP systems immensely useful, but only in cornering management who seem to delight in being specious and unordered. Implementing ERP can be a complete pain as a it so frequently shows how illogical a lot of companies 'business logic' is. For some reason the ERP system gets the blame for not being able to generate a profit out of chaos.
CRM is really a small part of ERP and generally meaningless without being linked to sales records but then the sales department often sell its ideas better internally than it does externally.
Making an evaluated decision is the right decision
In a large enterprise with multiple business areas, there are usually different business/workflow needs. The question of whether to integrate existing processes or absorb into the enterprise ERP infrastructure often appears to come down to short term budget £££ and potential to disrupt or change existing business process (always seen as risky for management) rather than a weighed evaluation of the pros/cons. IUMHO, any evaluation of an ERP path which aligns with business need at the time and guestimated expansion is the right choice as it will lead to a more coherent business and all the associated benefits.
RE: The SaaS offerings - fantastic instant gain for businesses which align closely with the product's own functionality. Not so good once you evolve and/or are forced to do most of the things you need to do outside the cloud.