United
Name for premium economy
Economy Plus, a.k.a. E+
Aircraft type
UA: 777, 767, 757, 747, 737, A320, A319
UAX: CRJ 700 (1 out of three versions), EMB 170,
Plain economy also exists on same a/c?
Yes
Seat improvements over economy (pitch, width, recline)
Extra 3-5 inches of pitch (34"), but same seat as in Economy
Food & drink improvements over economy
None
IFE improvements over economy
None
Baggage allowance
Same as plain economy.
On the ground (check in, lounge access, priority boarding)
Nothing extra
Enhanced mileage earning?
No.
How to get into it
At least one of the following:
- At least Silver Member of any Star Alliance airline
- Full fare economy ticket (Y/B)
- Buying upgrade at check-in
- Buying E+ - pass
- Asking nicely at check-in (does not always work

)
Please let me know if I missed something.
David