It is still beta so there will be some chances of bugs, lag, etc. I am running iOS 11 PB on my 6s but for me it's got a bit of lag, a few application crashes and the battery life can be dicey. However it is not my daily driver. Overall, it's up to you. I have heard from some it runs rather well on the 10.5.
I also just bought a 10.5 ipad pro and as soon as i got home i installed ios 11 pb on it and man this thing is solid for a beta. Of course ill get some small glitches here and there but nothing major. ios was built for the new ipad, once you try it you won’t want to go back