You've hit all the primary points:
1) Higher operating cost due to tube replacement and increased AC draw
(unless you're coming from Class A solid state, in which case the AC use will
be comparable if the wattage of the amps are similar). 300B tubes are among
the costliest to replace.
2) More hands-on maintenance: biasing, checking and replacing tubes (be
sure to purchase a tube tester). Biasing is easy.
3) The amp's sound will slowly change as the tubes age, versus a solid state
amp's sound remaining constant. You may or may not notice the change in
sound over time.
1) Higher operating cost due to tube replacement and increased AC draw
(unless you're coming from Class A solid state, in which case the AC use will
be comparable if the wattage of the amps are similar). 300B tubes are among
the costliest to replace.
2) More hands-on maintenance: biasing, checking and replacing tubes (be
sure to purchase a tube tester). Biasing is easy.
3) The amp's sound will slowly change as the tubes age, versus a solid state
amp's sound remaining constant. You may or may not notice the change in
sound over time.