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.
iOS 11 DB2 actually ran faster on my 10.5 than iOS 10.3.2. DB3 was slightly slower. DB4 is slower still. However, still pretty fast. Just nowhere near as fast as 10.3.2. While DB2 was even faster.
iOS 11 DB2 actually ran faster on my 10.5 than iOS 10.3.2. DB3 was slightly slower. DB4 is slower still. However, still pretty fast. Just nowhere near as fast as 10.3.2. While DB2 was even faster.
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