I have an Arrma Outcast and I love it, it gets bashed to hell and keeps coming back for more. Like all RC's Arrma need a little tweaking i.e stock servo is rubbish but that is soon rectified by swapping in something better. Reading on various forums and Facebook pages, Horizon Hobby have been very quick in replacing broken parts under warranty.
As for the spares, yes they are a bit thin on the ground but they are slowly coming through. I usually try horizonhobby.co.uk, modelsport.co.uk and wheelspinmodels.co.uk. Ebay is also very good for spares if you don't mind buying from the USA or Germany. jennysrc in the USA have a website and are on ebay as well and they are a breakers of new rc's and their prices are very good, though there is the wait and possible custom charges