replacement for rf amp.

These are some of them:

-Supply voltage and current consumption
-Output Power and Input Power
-Linearity
-Gain
-Frequency range and Bandwidth
-Power Control Range (if exist)
-Efficiency (if is important)

If it is used on cell phone.
You should take care
-power ramping coefficient
-band select timing
-Tx enable timing
-Front-end enable timing
-Input level range

It depends on which field is based the application.
In my field for example are very important:
1) frequency range
2) Output power
3) Harmonics
4) Maximum input power
5) power supply voltage and current
6) Dimensions and shape
7) Operating temperatures
8) Vibrations spectrum
9) Altitude
10 ) Maximum antenna mismatch and mismatch protection
11) Type of modulation

Mandi