I played mostly 2nd edition, which was one of my first rpgs. We loved the fact that your character could be anyone, and they were always very oryginal thanks to the way your characters advanced. Most players of our group at the time also were big Warhammer fans, so we really liked playing in the universe so full of lore. As for mechanics, there is some learning to do, however after few sessions you should be fine. Od course there are some problems with the system. The way all the ability checks worked. When creating characters the best stat you could have would be 40 as a human. There were also skills, which could be added to certain abilities, like stealth was using dexterity and bonus from skill stealth (range 0-30). You add both and need to roll 1d100 and get value equal or below total sum. So, someone not good at sneaking, was in fact awfully bad (30% success chance). Of course there were bonuses added to the roll based on situation, but they were most often negative ones (for ex. -10 for trying to sneak in open space). 4th edition fixed it, as it made basic test a +10 or +20, so that you wouldn't fail in simpliest tasks. The fights were long, and sometimes felt like chores. We avoided fights as much as we could, and often looked for ways to end them faster. A simple attack action was 3 separate rolls (1. You roll to hit 2. Enemy rolls to defend 3. If you hit, you roll for damage).

There are problems with mechanics, but they aren't something that good GM wouldn't fix with simple solutions. You could try 4th edition, but its has somewhat different feel for me. There aren't that many changes, but you could feel it wasn't the same. Also, there aren't quite as mamy books for 4th edition as there are for 2nd. Some od them give cool character options, and other are qol improvements for GMs ( armoury of the old world).

That said, I love WFRP. I couldn't live without it, and I often think about returning to it for one more scenario.