I’ve used 3G Internet on three mobile operator networks in the UK now: O2, Orange and T-Mobile. I use SSH quite a lot and have used it over each of those 3G networks in several sites in Nottingham, Loughborough and further afield in Grimsby. I get the same experience in each of those locations, and seemingly wherever else I go in the country, including Bonnyrigg recently.
SSH over the 3G networks of O2 and Orange is frustratingly laggy, but just about usable. On the other hand, SSH over T-Mobiles 3G network is pretty much the same as over a wired broadband connection and a joy to use.
Until I went with T-Mobile I just assumed that the latency I was experiencing was a limitation of 3G in general and accepted it, but it’s not. If you’re experiencing any sort of latency on your 3G connection, it’s because of your signal level, or something else about your networks implementation or location, it’s definitely not a limitation in 3G it’s self.