Points on Vodafone
When I had to make a decision regarding data for my company around two years ago, I had no choice but to choose Vodafone. This was because we had to have the best coverage as I did not know where the site staff were going to be in the UK. Scotland is still sketchy, but overall it has been a resounding success, especially since the uploading capability was an important factor.
I know a couple of 3 users that have used it for business and they have purportedly had very little problem with them, but they have always used them in strong 3 areas. I did not know about the Orange partnership with 3, which makes the argument to use them even stronger since they undoubtedly win on price.
My biggest beef with all of them is the European tariff and ROW. What were OFTEL thinking when they only targeted mobile calls and texting when it was obvious that the real money was going to be in data in the future? £3 per Mb for Orange is a criminal amount to charge for data, but there isn't a straight forward way to get a pay-as-you go data dongle for your country of choosing. T-mobile and 3 had an offer on their Italian sites for pay as you go dongles at very sensible rates, but I couldn't buy it in the UK and then use it when I got there. I don't care that it is a different division of the same company, it IS the same company. I couldn't get anywhere with Vodafone.
Someone could make some serious money for those big business travellers out there, if they could consolidate charges for data regardless of which country they were in.