I gave it a pretty rigorous road test a while back and while my opinion's not changed since then (Voda better for train use, 3 has the edge on price / contract stuff) there's a couple of things I'd like to add on the subject of les dongles, more generally.
From a hardware point of view there's just one final hurdle - can you just make it plug and play? I mean do I have to activate the application, Ok the connection, enter my password and *then* click connect on the phone icon in my toolbar (this on a Mac).
But niggles aside, no one should be without a dongle in this day and age - especially in the UK.
I shared my spare dongle with a colleague, who jokingly compared it - as I wrested it from his hands - to an extremely addictive substance. Without really noticing it, he'd very quickly got used to being able to hook up his laptop to the web wherever he was - and get a good broadband connection while he was at it.
There was a moment when we talked about him giving it back and we were about to get off the train when I realised he still had the thing.
Felt a bit like that moment in Lord of the Rings when Gandalf has to get all stern with Bilbo about giving the ring back. I swear my soon-to-be-3G-cold-turkey colleague was a beat away from calling it his "precious"...
Dongles are so cheap and so fast, while WiFi is so erratically free in this country that, for most people who carry a laptop I would recommend a dongle right now...