I think the reason most die hard Glock fans don't like the Gen 4 is because some of the early ones were having failures and they're pissed that Glock made changes to a platform that was working very well already.
People who previously didn't like Glocks like the Gen 4 because with the adjustable back straps it can fit most anyone now.
I have Gens 3 and 4 19s.
The Gen 4 has had 2 malfunctions in 2000 rounds, one was a stove pipe and the other was a failure to fire.
The failure to fire happened during a match first shot after a mag change. I pulled the trigger and it just clicked so I slapped the mag and racked the slide because I thought I didn't get the mag seated properly, but as I racked the slide I saw a round go flying. I looked for it after I finished that run and the primer didn't have any marks on it at all. I guess it must have had some debris in the striker channel, I've had no problems since and that was about 500 rounds ago.
I have a friend that bought a Gen 4 G19 the same time I bought mine and he has had about 3 stovepipes in 1500 rounds.
I like the Gen 4, but I am more accurate and faster with my Gen 3, I guess my Gen 3 is just like an old comfortable pair of blue jeans.
I think you can still get the Gen 3, but you can pick them up used all the time for around $450.
This shows a Gen 3 in the pic, but I would call to clarify.
http://www.budsgunshop.com/catalog/product_info.php/cPath/21_43/products_id/13716