Yes, I have suffered for the past 2 years with O2's ridiculously slow and unreliable data speeds, their network is becoming unusable for me both here in Worcestershire and in London (which I travel between frequently for work).
I luckily have 2 sims, an O2 sim and a Three sim, everytime Three out performs O2 in performance, speed, and reliability. To be honest no matter where I am in the country Three is always the better network.
Unfortunately, there is no hope whatsoever that O2 will upgrade their network infrastructure, start using better technology and utilise all their spectrum like Three does, a move that would mean ditching what they currently use which are slower long range masts and/or antennas, outdated infrastructure, and poor spectrum utilisation, so don't expect it to improve anytime soon, and actually you can expect it to get worse when O2 are forced to switch off their 2G and 3G networks next year.
I have a sense that unless O2 bring themselves upto at least the same speed as EE or Three then we may see them leave the UK cellular space in the not so distant future because the other major networks are leaps and bounds ahead of them and set to get even better while O2 remain quite stagnant in terms of upgrades and improvements to their network.
I really hope O2 wise up and upgrade the masts, network infrastructure and speeds to at least match the competition from the other major networks like EE, Three, and Vodafone but it doesn't seem likely.
