Do you recommend a bubble level for a sight? If so why? Thanks

Yes........If the sight comes with a third axis adjustment and it's set properly, it can mean hitting the vitals of hitting the shoulder on hill shots, that is, shots where the target is on a different horizontal and vertical plane.

An example of this is when your on a hill side and the deer is 10 feet below you and 20 yards to one side. The level definately comes in handy then.

Here is my ignorant response. After all there years bowhunting that is one gadget I have not had on my bow. I'm always thinking about my bow being level and I guess I've done a good job setting up and shooting it at level. If I had to do it all over again, I would use the level.
Good luck.

i have been shooting for about 5 years now and last year i got a new sight with a level and i use the level at the range when i am shooting over 25 yards. other than that i dont see a difference. and that level when hunting is one more thing to worry about when your trying to shoot the 15 pointer !

I recommend to all my customers that they use a level at shots over 25-30 yards. On an average, there will be an 8" left or right difference at 40 yards if you're off level by 1/2 bubble. The difference depends on how far apart your sight is over your arrow. The higher your sight, the more differnce there will be.

You would be surprised as to how easy it is to 'cant' your bow on uneven ground or treestand. It can become more of a problem if your bow isn't balanced/stabilized properly. We spend a lot of time getting our customers' bows balanced/stabilized.

I bought a Vital Bow Gear 3 Ring Trappers sight which has a bubble level on the first pin ring. First thing I did after installing the sight was remover the first sight ring with the bubble. I shoot my bow an aweful lot to not know when it's level. IMO the bubble level is one more thing that can break your concentration while you're waiting at full draw for your shot to materialize. I'm not knocking those of you who use one but to me it's overkill. I draw my bow, I anchor, I settle the pin and then launch the arrow. I can honestly say I don't worry or think about canting my bow. (this coming from a guy who shoots a 30" ATA bow go figure)

From my short experience with them they are great, but make sure you get one with a 3rd axis adjustment. Or you are gonna find out like I did that when shooting down or up your level is gonna make you shoot left or right. I have the Copper John 5 pin Hunter and it doesnt have the adjustment for the 3rd axis. So I dont use my level for shots from a tree or uphill or downhill.