I remember the sinking feeling when I heard Arriva had won the Wales & Borders franchise in 2003.
They had just lost the RR North East franchise (to Serco/Abellio, as Northern), and were also about to lose Merseyrail (also to Serco/Abellio).
However, they got those franchises by buying out MTL who were in serious trouble, for which they deserve industry thanks.
They took over in my neck of the woods from First North Western, who had given up (First withdrew from the W&B competition to concentrate on TPE).
Despite the low expectations, I think they integrated the 3-4 separate parts of the W&B franchise successfully and became a professional if unexceptional outfit.
The main problem was that the no-growth franchise was twice the length it ought to have been, so they marked time from about 2010 onwards.
Their real job was to reduce the W&B subsidy, which it did pretty successfully, with better financial returns than expected for themselves and DfT/WG.
Transfer of franchise management from the SRA to WG didn't change much, apart from Gerald and a decent facelift of 158s and 150s.
I didn't much care for the redirection of services towards Cardiff, including stealing our (ex-FNW) 175s and reducing through services via Crewe.
They never had any scope for a major change of rolling stock, and we will still be paying for that for another 5 years.
It was telling that Arriva didn't win any other new franchise until XC, and since then they have only won Northern.
The takeover by DB gifted them Chiltern, 50% of LO and Tyne & Wear Metro which had been won by DB Regio, to make them a significant UK rail player.
ATW was profitable throughout, and at times bailed out the black holes at XC and Chiltern until they were turned round.
They don't seem hot on innovation, and their franchises are now steady-state (we'll see what happens at Northern, the only one with major investment).
They lost out on the competitions for ICEC and ICWC, and didn't make the short-list for HS2 services (WCP).
They took over LNWR as a cross-TOC rolling stock maintainer, now Arriva Traincare, and it seems to do a good job for several TOCs.
We still don't know why they declined to bid for new Wales & Borders, maybe because DB is losing interest in UK operations.
Nor did they become in any shape or form a recognisably DB operation (ie German-like).
They still seem to be, as they started 15 years ago, basically a bus operator with a rail arm.
But when you see the events at National Express, Govia and Stagecoach franchises, maybe their steady-as-she-goes approach is not a bad one.
But again, it all might all turn sour at Northern.
I do agree that they have very friendly staff, at least until they started enforcing the "buy before you board" mantra.
Over the years they have also manipulated fares to their advantage, although that is common TOC practice.
Off-peak fares are now significantly higher/more restricted than they used to be (relative to the regulated fares).
We'll have to see what Keolis Amey do for us.