I won't pile-on about the plastic inconsistencies and razor-flash issues, as these are well-documented. I will only say that these types of issues are a HUGE pet-peeve of mine.
Here are my experiences with Gateway's mids and drivers. As a general rule, their Mids are relatively shallow-rimmed and fast. They feel like a mid/driver hybrid in the hand. Players with good snap can make them fly as such, but players without the ability to put crazy spin on them will find that they fly with less glide than many of the other discs on the market.
Element: like a beat Roc without the reliable stability. Flies unlike any other disc when it's seasoned. With a good snap on a steep hyzer, it'll travel 90% of its flight dead straight, while constantly performing a slow turnover, and then finish right very late, right as it's about to fall out of the air. Super unique shot. It turns over very slowly, but it doesn't stop turning over, and the turn doesn't seem to affect the flight until the very last 20-10%. Quite possibly the best tunnel-with-a-very-late-right-turn mid out there. Also a great disc for finesse sidearm upshots.
Element-X: a more stable element, they were crazy to get rid of this mold. Not that it would make my bag over a Roc or Buzzz, but because it was their best mid they had.
Warrior: a lot like a Whippet. Or a faster, but less glidey Drone. Beats into a flight similar to a brand-new max weight Glow Buzzz, but with less glide.
Sabre: a glideless leopard. Very controllable, very straight when thrown well, but needs a lot of height to get the distance that most discs can get thrown normally.
Apache: like a very domey Wraith. Slightly overstable when new, beats into a decent turnover S-curve driver. The dome on the two I've thrown was very high. Made it a bit uncomfortable in the hand.
Illusion: like a Destroyer with less glide. Power players can make these things go.