I have a G15 (original) and would never give it up. For me:
G1 party attack
G2 Pet attack only until in combat, then all attack
G3 Healer heal whoever has aggro
(90% of play is with these keys)
G4 PPT (push to talk on vent or WOW)
G5 Flying mount
G6 Ground mount
G7 Instant DPS movement (for DPS on the move in PVP)
G8 Random depending on group (hunters it is freezing trap, DKs and pallys it is taunt, locks it is deathcoil) all on round robin
G9 Spell Interrupt
G10-G12 Not used to much
G13 Buff (Smartbuff really helps to put buffs up)
G14 Jama-use 1
G15 Alts movement backward (used to stop them or move out of stuff)
G16 Accept All
G17 Jama-use 2
G18 Alts movement forward

I just got a X-Keys USB stick. I love it, just need to figure out where to put it. I use it for stuff I wish I could use Jamaba macros for. I want to do one thing on my main and have the alts do it, not keybind 16 things for seldom used stuff. I just want an easy /jamba-team LeaveBG or /Jamba-macro-healset to put on my healing set for my pallies, or /jamba-team-hearth. They don't need to be fancy, just simple stuff I use. I have used HKN to broadcast that in the past, and it worked okay, but now that the chat channel gets remembered, it locks in "/" slash so the next commands mess up. So I started up jamba-macro and made macros, bound them to jacked up keys CTRL-SHIFT-G, CTRL-SHIFT-H, etc and put them on my Xkeys.
Xkeys 1, invite
2) hearth
3) leave BG
4) blank
5) Outfitter BG set
6) Outfitter norm set
7) blank
8) Hunter pets 3 (stealth kitties for PVP), it is fun to sneak up with 5 cats they can't see (all Gondria)
9) Hunter pets 4 (all chimera, they have ranged slow and it is ROCKS hard, really fun)
10) blank
11-16) Jamab-use 1-5