I purchased an Excalibur Phoenix package that included 150 gr field points which I have found to be extremely accurate: even shooting off-hand I can expect the bolts to group within 1" out to 30 yards.
In preparation for hunting season I purchased the Excalibur recommended 150 gr "bolt cutter" fixed blade broadheads: shooting off-hand I am able to group within 3" out to 30 yards. They are not quite as accurate as the field-points but plenty accurate enough for hunting.
While the crossbow would likely remain accurate to 40 yards and beyond, I have no intention of shooting over 30 yards: the noise from the shot is so loud (compared to my Hoyt compound bow) that I am concerned about the deer "jumping the string" before the bolt arrives.
Practically, 30 yards is plenty for my typical opportunities. I took my first deer with the crossbow (a doe) with a broad-side shot at 15 yards on my second day out in the early PA season. It was a double lung pass-through with a massive entry and exit wound from the bolt-cutter broadhead: I found the bolt with the broadhead buried in the dirt the next morning. The doe ran about 35-40 yards and then collapsed.
As with the compound bow, distance estimation is critical for the crossbow: I used the 20 yard cross-hairs for the 15 yard shot and hit about 1 1/2" higher than I aimed. However, the crossbow accuracy with the bolt-cutter broadheads gives me confidence that I will make a kill shot (it also helps that there is very little left/right deviation with the crossbow as compared to a compound bow shot with less than perfect form).