I have the Tippmann. It really is a cracker of a rifle, all alloy, and with a working forward assist and bolt release. What I particularly like about it is that it is built as a 'true' AR15 style rifle in that the large main spring is actually housed and operates within the buffer tube so the only working piece inside is the solid one-piece bolt - as I say, a true AR15 rifle, not a 'lookalike'. It replaced a GSG STG44 'lookalike' which has the mini-bolt mounted on an alloy rail carriage internally as many .22's do. And the bolt/carriage assembly destroyed itself three times and, after the third time the importers/GSG gave up and scrapped it! I lost faith in this Heath Robinson 'toy' solution and instead decided to buy something built properly hence the Tippmann.
It's had thousands of rounds through it and loves Mini-Mags but is perfectly happy shooting and cycling subsonic hollow points flawlessly. The buffer tube is Milspec and will accept AR15 butts and other bits (mine is fitted with an aftermarket Magpul butt), the plastic open sights are actually excellent, the rifle has a proper steel barrel (not a liner), it operates flawlessly and always has, and it strips as an AR ie two captive pins - one to 'break' the rifle and remove the bolt, and the other will allow the upper and lower to be separated. It came with two 20rnd polymer mags and these have polymer feed lips which wear quickly - however the latest 25rnd mags (available from Riflemags) have steel feed lips and these are superb. I find the trigger just perfect and the 'thwack' or 'ting' when fired is simply because you have a proper bolt flying back and forth against a proper mainspring. I use mine with open sights at 100yds on club range days or with subsonics and scope for rabbits.
Some YouTube vids on them and 22Plinkster has a review.