I actually use vodafone empresas and have 6 lines with them and have no problems with them at all.
In case you did not know (and I did not until my new vodafone guy told me after he checked my tarifs), they actually do a 3G Tarifa Plana for business which consists of 5GB of bandwidth per month at 3.5MB speed and if you exceed that, they throttle you down to 250kbps, which sounds awful, but if you use your phone for email and general web browsing its not too bad.
I have my phone checking my email every hour 24/7, and I get ALOT of email (around 500 per day...thats without any spam) and the speed is decent.
This costs a flat fee of €50 per month and if you are clever enough to figure out how to connect your laptop to your phone with bluetooth and use the phone as the 3G modem, then basically you dont have to sign up for their stupid dongle or the red pcmcia card.

My vodafone guy is Joey from Tanuki Data who is also a Mac Specialist but does vodafone on the side and can help you with vodafone related stuff if you are on a business tariff.
His number is +34 646 353 935 and he is English and speaks native Spanish.
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