Many blues pianists stick to relatively simple keys – C, F and G. Being able to play blues in E major (and A major, which is similar) is very useful, because it makes it very easy to work with guitarists if you happen to play in a band.
It’s actually easier than it looks, because the E blues scale uses a lot of white notes on the piano keyboard. So although you get a sound that’s distinctively different from a blues in C or F, it’s not a lot more difficult to play. You just need to be comfortable working in a slightly different key. Although you will mostly stay away from the E major scale, this is yet another area where a basic familiarity with piano scales will really come in handy. Being able to readily adapt your fingers to different positions and situations on the piano keyboard is a skill that comes with practising scales regularly – and it’ll really help you here.
The one thing you have to do a little is adapt the riffs and licks you’re used to playing in easier keys, especially the ones that involve crush notes. In a few cases you’ll find that crushes are harder, because instead of going from a black note to a white note you’ll be doing it the other way around, but if you know your way around the piano – and a bit about how blues scales work – you shouldn’t have too much trouble figuring this out. Other licks are simply not that comfortable in different keys. Of course, the flipside of that is that keys like E and A offer unique licks giving a distinctive sound.
As a pianist, being able to improvise blues (or rock n roll, or boogie, or R n B, or funk, or whatever) in a guitar-friendly key is miles better than reaching for the transpose button on your keyboard — which is cheating, and, oddly enough, might result is an unauthentic sound.
As with every aspect of piano blues, and piano improvisation in general, these skills need to be practised heavily if you’re going to master them. However, while you’re practising be sure to experiment, play around, and develop your own sounds. The point about being good blues pianist is that you are an individual and you should strive for an individual style at the piano keyboard.